Water resistance imparter, ink composition, reactive fluid, and method of ink-jet recording with two fluids

ABSTRACT

Disclosed is a cationic water-soluble resin which comprises a (co)polymer of, in formula (I), repeating units (a) represented by formula (a) and repeating units (b) represented by formula (b), the content of the repeating units (a) in the (co)polymer being 100 to 0% by mole, the (co)polymer having in its molecule a carboxyl-containing group as one of the terminal groups and an aromatic ring-containing group as the other terminal group. The addition of this resin to ink compositions can realize the formation of images possessing excellent waterfastness and lightfastness and having no significant feathering or color bleeding. Likewise, the addition of this resin to a reaction solution for ink jet recording involving the deposition of two liquids, an ink composition and a reaction solution, onto a recording medium, can realize the formation of images possessing excellent waterfastness and lightfastness and no significant feathering or color bleeding.                    
     wherein R 1  represents hydrogen or methyl; R 2  and R 3  represent C 1-3  alkyl; R 4  represents hydrogen or methyl; R 5 , R 6 , and R 7  represent C 1-3  alkyl; Z −  represents a counter ion; and k and 1 are each 1, 2, or 3.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a waterfastness-imparting agentcomprising a cationic water-soluble resin having a specific structure,an ink composition containing the waterfastness-imparting agent, areaction solution containing the waterfastness-imparting agent, and inkjet recording methods using the same.

2. Background Art

Realization of images having good waterfastness and lightfastness and,at the same time, having no significant feathering or bleeding isimportant for printing of images using ink compositions.

In order to realize good waterfastness, as exemplified below, acombination of a cationic resin with an anionic dye has hitherto beenused.

For example, Japanese Patent Laid-Open No. 119280/1987 discloses an inkcomprising a hydroxyethylated polyethyleneimine polymer and a dyecomponent. This publication describes that the combination of thehydroxyethylated polyethyleneimine polymer with the dye component candevelop waterfastness. Japanese Patent Publication No. 91494/1995discloses an ink comprising a hydroxyalkylated polyallylamine polymerand a dye. This publication describes that the combination of thehydroxyalkylated polyallylamine polymer and the dye can developwaterfastness. In these two inks, however, a further improvement isrequired to ensure satisfactory waterfastness of printed images becausehydroxyalkyl groups having high hydrophilicity are contained in thepolymer.

Japanese Patent Laid-Open Nos. 255876/1990, 296878/1990, and 188174/1991disclose ink compositions comprising a polyamine, with a molecularweight of not less than 300, having primary amino groups, an anionicdye, and a stability-imparting agent. These publications describe thatthe combination of the primary amino group with the anionic dye candevelop waterfastness. Disadvantageously, however, the resins used inthese publications strongly attack the dye. Specifically, according tostudies conducted by the present inventors, for example, when this inkis allowed to stand at high temperatures, in some cases, the dye isdecomposed or otherwise the photodecomposition of the print isaccelerated to render the lightfastness lower than that of an inkcontaining only the dye.

Japanese Patent Laid-Open No. 305011/1995 discloses a water-base inkcomprising a basic water-soluble polymer, an anionic dye with thecounter ion being a volatile base, and a buffering agent with thecounter ion being a volatile base. This publication describes that, inthe ink, the volatile base prevents the dissociation of the polymer and,after printing, the volatile base on paper is evaporated to allow asalt-forming reaction between the polymer and the dye to proceed,thereby developing waterfastness.

Japanese Patent Laid-Open No. 238783/1987 discloses an ink jet recordingsheet comprising a homopolymer of an acid salt of diallylamine or anacid salt of monoallylamine or a copolymer of the acid salt ofdiallylamine with the acid salt of monoallylamine. According to thepublication, the advantage of this recording sheet is that the polymerreacts with the dye to become insoluble on the recording medium todevelop waterfastness. However, since the ink per se does not havewaterfastness, use of a recording medium other than described in thepublication cannot develop the waterfastness.

Ink jet recording is a printing method wherein droplets of an inkcomposition are ejected and deposited onto recording media, such aspaper, to perform printing. This method has a feature that images havinghigh resolution and high quality can be printed at a high speed by meansof relatively inexpensive apparatuses. In general, the ink compositionused in the ink jet recording comprises water as a main component and,added thereto, a colorant component and a wetting agent, such asglycerin, for preventing clogging and other purposes.

Furthermore, regarding the ink jet recording method, the application ofa polyvalent metal salt solution onto a recording medium followed by theapplication of an ink composition containing a dye having at least onecarboxyl group has been recently proposed (for example, Japanese PatentLaid-Open No. 202328/1993). The advantage of this method is that thepolyvalent metal ion combines with the dye to form an insoluble complex,the presence of which can offer an image having waterfastness and highquality free from color bleeding.

Further, the use of a color ink comprising at least a surfactant forimparting a penetrating property or a solvent having a penetratingproperty and a salt in combination with a black ink capable of beingthickened or agglomerated through the action of the salt has beenproposed in the art (Japanese Patent Laid-Open No. 106735/1994). Theadvantage of this method is that high-quality color images having highimage density and free from color bleeding can be yielded. Specifically,an ink jet recording method has been proposed wherein two liquids, aliquid containing a salt and an ink composition, are printed to realizegood images.

Other ink jet recording methods, wherein two liquids are printed, havealso been proposed, for example, in Japanese Patent Laid-Open Nos.240557/1991 and 240558/1991.

SUMMARY OF THE INVENTION

The present inventors have now found that the addition of a cationicwater-soluble resin having a specific structure to an ink compositionand a reaction solution for use in ink jet recording involving thedeposition of two liquids, an ink composition and a reaction solution,onto a recording medium can realize good images, especially imagespossessing excellent waterfastness and lightfastness, and having nosignificant feathering or bleeding. The present invention has been madebased on such finding.

Accordingly, it is an object of the present invention to provide awaterfastness-imparting agent which can realize an ink composition and areaction solution for use in ink jet recording method involving thedeposition of two liquids, an ink composition and a reaction solution,onto a recording medium, the method being capable of realizing imagespossessing excellent waterfastness and lightfastness and having nosignificant feathering or bleeding.

It is another object of the present invention to provide an inkcomposition which can realize images possessing excellent waterfastnessand lightfastness and, at the same time, having no significantfeathering or bleeding.

It is a further object of the present invention to provide a reactionsolution for use in ink jet recording using two liquids and an ink jetrecording method using the same, the method being capable of realizingimages possessing excellent waterfastness and lightfastness and havingno significant feathering or bleeding, especially having no significantcolor bleeding.

According to a first aspect of the present invention, there is provideda waterfastness-imparting agent comprising a cationic water-solubleresin, said cationic water-soluble resin comprising a (co)polymercomprising, in formula (I), repeating units (a) represented by formula(a) and repeating units (b) represented by formula (b), the content ofthe repeating units (a) in the (co)polymer being 100 to 0% by mole, said(co)polymer having in its molecule a carboxyl-containing group as one ofthe terminal groups and an aromatic ring-containing group as the otherterminal group:

wherein

R₁ represents a hydrogen atom or a methyl group;

R₂ and R₃, which may be the same or different, represent a C₁₋₃ alkylgroup;

R₄ represents a hydrogen atom or a methyl group;

R₅, R₆, and R₇, which may be the same or different, represent a C₁₋₃alkyl group;

Z⁻ represents a counter ion; and

k and l which may be the same or different, are each 1, 2, or 3.

According to a second aspect of the present invention, there is providedan ink composition comprising at least the cationic water-soluble resinas defined above.

According to a third aspect of the present invention, there is provideda reaction solution for use in ink jet recording method involving thedeposition of a reaction solution and an ink composition onto arecording medium to perform printing, the reaction solution comprisingat least the cationic water-soluble resin as defined above.

According to a fourth aspect of the present invention, there is providedan ink jet recording method comprising the step of depositing an inkcomposition and a reaction solution onto a recording medium to performprinting, the reaction solution containing a waterfastness-impartingagent which comprises the cationic water-soluble resin having a specificstructure as defined above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing an embodiment of an ink jet recordingapparatus usable in practicing the present invention, wherein arecording head is provided separately from an ink tank and an inkcomposition and a reaction solution are fed into the recording headthrough an ink tube;

FIG. 2 is an enlarged view showing a nozzle face of a recording head,wherein 1 b designates a nozzle face for a reaction solution and 1 c anozzle face for ink compositions;

FIG. 3 is a diagram illustrating ink jet recording using the recordinghead shown in FIG. 2, wherein numeral 31 designates a reactionsolution-deposited region and numeral 32 a printed region where an inkcomposition has been printed on a reaction solution-deposited portion;

FIG. 4 is a diagram showing another embodiment of the recording headusable in practicing the present invention, wherein all ejection nozzlesare arranged in the lateral direction; and

FIG. 5 is a diagram showing another embodiment of the ink jet recordingapparatus usable in practicing the present invention, wherein arecording head is integral with an ink tank.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Waterfastness-imparting AgentRepresented by Formula (I)

The waterfastness-imparting agent comprising a cationic water-solubleresin having a specific structure according to the present invention(hereinafter referred to as “waterfastness-imparting agent”) is a(co)polymer comprising, in formula (I), repeating units (a) representedby formula (a) and repeating units (b) represented by formula (b), thecontent of the repeating units (a) in the (co)polymer being 100 to 0% bymole, the (co)polymer having in its molecule a carboxyl-containing groupas one of the terminal groups and an aromatic ring-containing group asthe other terminal group. According to the present invention, the“waterfastness-imparting agent” means an additive which, when added to asolution which should be waterfast in a dried form, can impart at leastwaterfastness to a dried product of the solution. Specifically, thewaterfastness-imparting agent means an additive which, when added to anink composition, can impart at least waterfastness to an image yieldedby the ink composition. Furthermore, it means an additive which, whenadded to a reaction solution can impart at least waterfastness to animage formed by the ink jet recording method involving the deposition oftwo liquids, the reaction solution and an ink composition, onto arecording medium to perform printing,.

The ink composition, to which the waterfastness-imparting agentaccording to the present invention has been added, can realize imageshaving no significant feathering or bleeding and having excellentwaterfastness. Further, since the colorant is strongly fixed onto therecording medium, the effect of realizing images having no significantfeathering or bleeding is significant.

Furthermore, the waterfastness-imparting agent according to the presentinvention, when brought into contact with an ink composition, isconsidered to break the state of dissolution and/or dispersion of acolorant, an optional resin emulsion described below, and otheringredients of the ink composition and to agglomerate them. Therefore,in the so-called “ink jet recording using two liquids,” when thiswaterfastness-imparting agent is added to the reaction solution, it isconsidered that the agglomerate can inhibit the penetration of thecolorant into the recording medium. As a result, images having highcolor density and free from significant feathering and significantunevenness of printing can be realized. Further, in the case of colorimages, uneven color mixing in boundaries of different colors, that is,color bleeding, can also be advantageously prevented.

In the waterfastness-imparting agent represented by formula (I), R₁ andR₄ may be the same or different and each independently represent ahydrogen atom or a methyl group. R₂, R₃, R₅, R₆, and R₇ may be the sameor different and each independently represent a C₁₋₃ alkyl group,preferably a methyl group. Most preferably, a combination is preferredwherein R₁ represents a hydrogen atom, R₂ represents a methyl group, R₃represents a methyl group, R₄ represents a hydrogen atom, R₅ representsa methyl group, R₆ represents a methyl group, and R₇ represents a methylgroup.

Z⁻ represents a counter ion, and Z preferably represents a halogen atom,that is, a fluorine, chlorine, bromine, or iodine atom, more preferablya chlorine atom.

In formula (I), k and 1 are each 1, 2, or 3, preferably 3.

Examples of carboxyl-containing terminal groups include groupsrepresented by formulae (II) to (V).

Examples of aromatic ring-containing terminal groups include groupsrepresented by formulae (VI) to (XVII).

When the waterfastness-imparting agent is added to the ink compositionaccording to the second aspect of the present invention, the content ofthe units (a) in formula (I) is 100 to 80% by mole, preferably 100 to90% by mole, more preferably 100 to 95% by mole. The two repeating unitsmay be present in a block or random form.

On the other hand, when the waterfastness-imparting agent is added tothe reaction solution according to the third aspect of the presentinvention, the content of the unit (a) in formula (I) is 100 to 0% bymole, preferably 80 to 0% by mole, more preferably 45 to 0% by mole. Thetwo repeating units may be present in a block or random form.

According to a preferred embodiment of the present invention, thewaterfastness-imparting agent has a number average molecular weight ofabout 1,000 to 10,000 as determined by gel permeation chromatography(hereinafter abbreviated to “GPC”).

Ink Composition

The ink composition according to the second aspect of the presentinvention is used in recording methods using ink compositions, forexample, ink jet recording, recording method using writing utensils,such as pens, and other various recording methods. Particularlypreferably, the ink composition according to the present invention isused in the ink jet recording method.

The ink composition according to the present invention basicallycomprises at least an alkali-soluble colorant, a water-soluble organicsolvent, water, a waterfastness-imparting agent comprising a cationicwater-soluble resin having a specific structure represented by formula(I). As described above, the ink composition with thewaterfastness-imparting agent according to the present invention addedthereto can realize images having no significant feathering or bleedingand having excellent waterfastness. Further, since the colorant isstrongly fixed onto the recording medium, the effect of realizing imageshaving no significant feathering or bleeding is significant.

The amount of the waterfastness-imparting agent represented by formula(I) added may be properly determined so that the above effect can beattained. The waterfastness-imparting agent is added preferably in anamount of about 0.2 to 20% by weight, more preferably about 0.5 to 10%by weight, still more preferably about 0.5 to 5% by weight, based on theink composition.

The alkali-soluble colorant contained in the ink composition accordingto the present invention is a dye or a pigment. The term“alkali-soluble” used herein means that the colorant can be dissolved inan alkaline medium. The water-soluble group contained in the moleculemay be an acidic or basic dissociative group or nondissociativefunctional group, or alternatively a plurality of kinds of these groupsare present in the molecule. Alkali-soluble colorants may be soluble inacidic solutions so far as they are soluble in alkalis.

The content of the colorant may be properly determined. For example, thecolorant is added preferably in an amount of 0.5 to 20% by weight basedon the total weight of the ink composition. This is because a colorantcontent falling within the above range can provide printed images havingsatisfactory optical density and permits the viscosity of the ink to beeasily adjusted to a value suitable for ink jet recording.

More preferably, the colorant is selected from organic dyes or organicpigments. Use of organic dyes or organic pigments is advantageous torealize high color density per weight and vivid colors.

Dyes are organic color materials soluble in water, and preferred dyesare those that fall into categories of acidic dyes, direct dyes,reactive dyes, soluble vat dyes, and food dyes according to the colorindex. Further, colorants, insoluble in neutral water, falling withincategories of oil-soluble dyes and basic dyes according to the colorindex may also be used so far as they are soluble in aqueous alkalisolutions.

On the other hand, pigments may be generally selected from those fallingwithin categories of pigments according to the color index. Althoughpigments are generally regarded as water-insoluble organic colormaterials, some pigments are soluble in alkalis and may be used in thepresent invention.

Examples of dyes and pigments usable herein include:

yellow dyes and pigments, such as C.I. Acid Yellow 1, 3, 11, 17, 19, 23,25, 29, 36, 38, 40, 42, 44, 49, 59, 61, 70, 72, 75, 76, 78, 79, 98, 99,110, 111, 127, 131, 135, 142, 162, 164, and 165, C.I. Direct Yellow 1,8, 11, 12, 24, 26, 27, 33, 39, 44, 50, 55, 58, 85, 86, 87, 88, 89, 98,110, 132, 142, and 144, C.I. Reactive Yellow 1, 2, 3, 4, 6, 7, 11, 12,13, 14, 15, 16, 17, 18, 22, 23, 24, 25, 26, 27, 37, and 42, C.I. FoodYellow 3 and 4, C.I. Solvent Yellow 15, 19, 21, 30, and 109, and C.I.Pigment Yellow 23;

red dyes and pigments, such as C.I. Acid Red 1, 6, 8, 9, 13, 14, 18, 26,27, 32, 35, 37, 42, 51, 52, 57, 75, 77, 80, 82, 85, 87, 88, 89, 92, 94,97, 106, 111, 114, 115, 117, 118, 119, 129, 130, 131, 133, 134, 138,143, 145, 154, 155, 158, 168, 180, 183, 184, 186, 194, 198, 209, 211,215, 219, 249, 252, 254, 262, 265, 274, 282, 289, 303, 317, 320, 321,and 322, C.I. Direct Red 1, 2, 4, 9, 11, 13, 17, 20, 23, 24, 28, 31, 33,37, 39, 44, 46, 62, 63, 75, 79, 80, 81, 83, 84, 89, 95, 99, 113, 197,201, 218, 220, 224, 225, 226, 227, 228, 229, 230, and 231, C.I. ReactiveRed 1, 2, 3, 4, 5, 6, 7, 8, 11, 12, 13, 15, 16, 17, 19, 20, 21, 22, 23,24, 28, 29, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 45, 46,49, 50, 58, 59, 63, and 64, C.I. Solubilized Red 1, C.I. Food Red 7, 9,and 14, and C.I. Pigment Red 41, 48, 54, 57, 58, 63, 68, and 81;

blue dyes and pigments, such as C.I. Acid Blue 1, 7, 9, 15, 22, 23, 25,27, 29, 40, 41, 43, 45, 54, 59, 60, 62, 72, 74, 78, 80, 82, 83, 90, 92,93, 100, 102, 103, 104, 112, 113, 117, 120, 126, 127, 129, 130, 131,138, 140, 142, 143, 151, 154, 158, 161, 166, 167, 168, 170, 171, 182,183, 184, 187, 192, 199, 203, 204, 205, 229, 234, 236, and 249, C.I.Direct Blue 1, 2, 6, 15, 22, 25, 41, 71, 76, 77, 78, 80, 86, 87, 90, 98,106, 108, 120, 123, 158, 160, 163, 165, 168, 192, 193, 194, 195, 196,199, 200, 201, 202, 203, 207, 225, 226, 236, 237, 246, 248, and 249,C.I. Reactive Blue 1, 2, 3, 4, 5, 7, 8, 9, 13, 14, 15, 17, 18, 19, 20,21, 25, 26, 27, 28, 29, 31, 32, 33, 34, 37, 38, 39, 40, 41, 43, 44, and46, C.I. Solubilized Vat Blue 1, 5, and 41, C.I. Vat Blue 29, C.I. FoodBlue 1 and 2, C.I. Basic Blue 9, 25, 28, 29, and 44, and C.I. PigmentBlue 1 and 17; and

black dyes and pigments, such as C.I. Acid Black 1, 2, 7, 24, 26, 29,31, 48, 50, 51, 52, 58, 60, 62, 63, 64, 67, 72, 76, 77, 94, 107, 108,109, 110, 112, 115, 118, 119, 121, 122, 131, 132, 139, 140, 155, 156,157, 158, 159, and 191, C.I. Direct Black 17, 19, 22, 32, 35, 38, 51,56, 62, 71, 74, 75, 77, 94, 105, 106, 107, 108, 112, 113, 117, 118, 132,133, 146, 154, 168, 171, and 195, C.I. Reactive Black 1, 3, 4, 5, 6, 8,9, 10, 12, 13, 14, and 18, C.I. Solubilized Vat Black 1, and C.I. FoodBlack 2. These colorants may be used alone or as a mixture of two ormore.

According to the ink composition of the present invention, water is amain solvent. Water may be pure water obtained by ion exchange,ultrafiltration, reverse osmosis, distillation or the like, or ultrapurewater. Further, water, which has been sterilized, for example, byultraviolet irradiation or by addition of hydrogen peroxide, is suitablebecause, when the ink composition is stored for a long period of time,it can prevent the growth of mold or bacteria.

The ink composition according to the present invention may contain anacidic material. Acidic materials usable herein include, for example,inorganic acids, such as hydrochloric acid, bromic acid, hydrofluoricacid, sulfuric acid, phosphoric acid, and nitric acid, and organicacids, such as acetic acid, propionic acid, n-butyric acid, iso-butyricacid, n-valeric acid, glycolic acid, gluconic acid, lactic acid, andtoluenesulfonic acid. The addition of these acidic materials to inks canfurther improve the waterfastness of printed images.

The ink composition according to the present invention can furthercontain a basic material. Examples of basic materials usable hereininclude: inorganic bases, such as sodium hydroxide, potassium hydroxide,lithium hydroxide, calcium hydroxide, barium hydroxide, strontiumhydroxide, radium hydroxide, berylium hydroxide, magnesium hydroxide,and ammonia; mono-, di- or tri-lower alkylamines, such as ethylamine,diethylamine, triethylamine, propylamine, dipropylamine,diisopropylamine, tert-butylamine, dibutylamine, diisobutylamine,isopropylamine, sec-butylamine, and pentylamine; lower alkyl lowerhydroxyalkoxyamines, such as 3-ethoxypropylamine and3-methoxypropylamine; lower alkyl lower alkoxyamines, such as3-ethoxypropylamine and 3-methoxypropylamine; mono-, di- or tri-lowerhydroxyalkylamines, such as 2-aminoethanol, 2-(dimethylamino)ethanol,2-(diethylamino)ethanol, diethanolamine, N-butyldiethanolamine,triethanolamine, aminomethylpropanol, and triisopropanolamine; andorganic amines, such as iminobispropylamine, .3-diethylaminopropylamine,dibutylaminopropylamine, methylaminopropylamine,dimethylaminopropanediamine, and methyliminobispropylamine. These basicmaterials can function so that the waterfastness-imparting agent and thecolorant can be stably dissolved and held in the ink composition. Forexample, when an ink is prepared using the waterfastness-imparting agentaccording to the present invention in combination with a specificcolorant, mere mixing is often insufficient for dissolution of theseingredients in the ink. The addition of the basic material permits thewaterfastness-imparting agent and the colorant to be stably dissolved inthe ink.

In the ink composition according to the present invention, the term“water-soluble organic solvent” refers to a medium which can dissolvesolutes of the ink, such as a colorant. Preferably, the water-solubleorganic solvent is selected from water-soluble solvents having a lowervapor pressure than water. In addition to solvents which are liquid atroom temperature, the following materials may be utilized as the solventaccording to the present invention: materials which are solid at roomtemperature and, upon heat melting, can function as a solvent; andmaterials which, when used in combination with aqueous solutions orother solvents, can function as a solvent. Examples of water-solubleorganic solvents include: polyhydric alcohols, such as ethylene glycol,propylene glycol, butanediol, pentanediol, 2-butene-1,4-diol,2-methyl-2,4-pentanediol, glycerin, 1,2,6-hexanetriol, diethyleneglycol, and dipropylene glycol; ketones, such as acetonylacetone;γ-butyrolactone; esters, such as diacetin and triethyl phosphate; loweralkoxy lower alcohols, such as 2-methoxyethanol and 2-ethoxyethanol;sulfur-containing compounds, such as thiodiglycol, dimethyl sulfoxide,and sulfolane; nitrogen-containing compounds, such as ethyleneurea,prolyleneurea, and 1,3-dimethyl-2-imidazolidinone; ethylene carbonate;propylene carbonate; furfuryl alcohol; and tetrahydrofurfuryl alcohol.Since the vapor pressure of the organic solvent is lower than that ofpure water, the content of the organic solvent in the ink does not lowereven when the drying of the ink proceeds at the front end of an ink jethead. As a result, the dissolving power of the organic solvent does notlower, and the ink can be stably kept.

The amount of the water-soluble organic solvent added may be properlydetermined. For example, the addition of the water-soluble organicsolvent in an amount of 5 to 50% by weight based on the total amount ofthe ink is preferred.

According to a preferred embodiment of the present invention, the inkcomposition according to the present invention may contain a cloggingpreventive selected from the group consisting of (1) water-solublehydroxypyridine derivatives, (2) chain or cyclic amide compounds, (3)imidazole derivatives, (4) hydroxy cyclic amine compounds, (5) azolecompounds, (6) azine compounds, (7) amidine derivatives, and (8) purinederivatives.

The addition of these clogging preventives can prevent ink from dryingat the front end of nozzles even under an extreme condition such that,for example, an ink jet recording apparatus is allowed to stand underhigh temperature and low humidity conditions for a long period of time.Further, even when the drying of the ink further proceeds to causesolidification, the solid present at the front part of the nozzles canbe redissolved by ink supplied from the rear part of the nozzle.Therefore, even after standing for a long period of time, printing canbe normally resumed in an early stage.

According to a preferred embodiment of the present invention, theclogging preventive is added preferably in an amount of about 1 to 40%by weight based on the ink composition.

(1) Water-soluble Hydroxypyridine Derivative

The water-soluble hydroxypyridine derivative usable in the presentinvention refers to a water-soluble compound wherein a hydroxyl grouphas been bonded to a pyridine ring either directly or through amethylene chain. Specific examples of water-soluble hydroxypyridinederivatives include 2-pyridinol, 3-pyridinol, 4-pyridinol,3-methyl-2-pyridinol, 4-methyl-2-pyridinol, 6-methyl-2-pyridinol,2-pyridine methanol, 3-pyridine methanol, 4-pyridine methanol,2-pyridine ethanol, 3-pyridine ethanol, 4-pyridine ethanol, 2-pyridinepropanol, 3-pyridine propanol, 4-pyridine propanol, a -methyl-2-pyridinemethanol, and 2,3-pyridinediol. They may be used alone or as a mixtureof two or more.

(2) Chain or Cyclic Amide Compound

The water-soluble chain or cyclic amide compound usable in the presentinvention is a chain amide derivative having 1 to 8 carbon atoms in itsmolecule, preferably a chain amide derivative having 1 to 6 carbon atomsin its molecule, and a cyclic amide derivative having 4 to 8 carbonatoms in its molecule, preferably a cyclic amide derivative having 4 to6 carbon atoms in its molecule. Specific examples of water-soluble chainor cyclic amide compounds include lactamides, methyl carbamate, ethylcarbamate, propyl carbamate, formamide, N-methylformamide, N,N-diethylformamide, N, N-dimethylformamide, acetamide,N-methylacetamide, N,N-dimethylacetamide, propionamide,N-methylpropionamide, nicotinamide, 6-aminonicotinamide,N,N-diethylnicotinamide, N-ethylnicotinamide, 2-pyrrolidone,N-methyl-2-pyrrolidone, 5-methyl-2-pyrrolidone,5-hydroxymethyl-2-pyrrolidone, δ-valerolactam, ε-caprolactam,heptolactam, pyroglutamic acid, N-methyl-ε-caprolactam, and8-propiolactam. They may be used alone or as a mixture of two or more.

(3) Imidazole Derivative

The imidazole derivative usable in the present invention is awater-soluble compound wherein a hydroxyl group, a carboxyl group, or alower alkyl (for example, a C₁₋₆ alkyl group, preferably a C₁₋₄ alkyl)has been attached to an imidazole ring. Specific examples of imidazolederivatives include imidazole, N-methylimidazole, 2-methylimidazole,2-hydroxyimidazole, 4-hydroxyimidazole, 5-hydroxyimidazole,pyrimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, histamine,histidine, imidazoleacetic acid, 4-methylimidazole, 4-imidazoleacrylicacid, 4,5-imidazoledicarboxylic acid, and pilocarpine. They may be usedalone or as a mixture of two or more.

(4) Hydroxy Cyclic Amine Compound

The hydroxy cyclic amine compound usable in the present invention is awater-soluble compound wherein a hydroxyl group has been attached to acyclic amine (preferably a five- or six-membered cyclic amine) eitherdirectly or through a methylene chain. Specific examples of hydroxycyclic amine compounds include 4-hydroxypiperidine, 3-hydroxypiperidine,2-hydroxypiperidine, N-methyl-3-hydroxypiperidine,N-ethyl-3-hydroxypiperidine, N-methyl-3-hydroxymethylpiperidine,N-methyl-2-hydroxymethylpiperidine, N-(2-hydroxyethyl)piperidine,2-(2-hydroxyethyl)piperidine, 4-(2-hydroxyethyl)piperidine,N-(2-hydroxyethyl)piperazine, N-(2-hydroxyethyl)morpholine,N-(2-hydroxypropyl)morpholine, N-(2-hydroxyethyl)pyrrole, pyrrolinol,N-(2-hydroxyethyl)pyrrolidine, N-methyl-2-(2-hydroxyethyl)pyrrolidine,N-(2-hydroxyethyl)ethyleneimine, 3-oxypyrazole, and 5-oxypyrazole. Theymay be used alone or as a mixture of two or more.

(5) Azole Compound

The azole compound usable in the present invention is a water-solublefive-membered heterocyclic compound having two or more hetero atoms inits ring with at least one hetero atom being nitrogen. In particular,the number of hetero atoms is preferably two or three. The hetero atomis preferably selected form nitrogen, oxygen, and sulfur. Specificexamples of azole compounds include 1,2,3-triazole, 1,2,4-triazole,1,2,3-triazole-4,5-dicarboxylic acid, 1H-1,2,4-triazole-3-thiol,benzotriazole, benzotriazole-5-carboxylic acid,1H-benzotriazole-1-methanol, pyrazole, tetrazole, oxazole,N-1-(4,5-dimethyl-2-oxazolyl)sulfanylamide, thiazole, 2-aminothiazole,2-thiazolecarboxyaldehyde, 5-thiazolemethanol, 1,2,3-thiadiazole,benzimidazole, benzimidazole-2-carbamic acid,(2-benzimidazolyl)acetonitrile, 5-benzimidazolecarboxylic acid,2-benzimidazoleethanol, 2-benzimidazolepropionic acid, and2-mercaptobenzimidazole. They may be used alone or as a mixture of twoor more.

(6) Azine Compound

The azine compound usable in the present invention is a water-solublesix-membered heterocyclic compound having two or more hetero atoms inits ring with at least one hetero atom being nitrogen. In particular,the number of hetero atoms is preferably two or three. The hetero atomis preferably selected form nitrogen, oxygen, and sulfur. The azinecompound may have a carboxyl group or a lower alkyl (for example, analkyl having 1 to 6 carbon atoms, preferably 1 to 4 carbon atoms) as asubstituent. Specific examples of azine compounds include pyrazine,pyrazinamide, hexahydropyrazine, 3-ethyl-2,6-dimethylpyrazine,pyrazine-2,3-dicarboxylic acid, pyrazinecarbonitrile,2,3-pyrazinedicarbonitrile, 2,3-pyrazinecarboxyamide,2,3-pyrazinedicarboxylic anhydride, pyrazine ethane thiol, triazine,cyanuric acid, methyl cyanurate, melamine, trithiocyanuric acid,pyridazine, 4-pyridazinecarboxylic acid, cytosine, cytosine-5-carboxylicacid. They may be used alone or as a mixture of two or more.

(7) Amidine Derivative

The amidine derivative usable in the present invention is water-solubleand is preferably a guanidine derivative. Specific examples of amidinederivatives include guanidine, 1-methyl-3-nitro-1-nitrosoguanidine,1-amyl-3-nitro-1-nitrosoguanidine, nitroguanidine, sulfaguanidine,guanidinoacetic acid, guanitidine, aminoguanidine, canavanine,argininosuccinic acid, arginine, and biguanide. They may be used aloneor as a mixture of two or more.

(8) Purine Derivative

The purine derivative usable in the present invention is water-soluble,and specific examples thereof include purine, purine riboside,2-amino-6-mercaptopurine, 6-(methylthio)purine riboside,6-benzylaminopurine, xanthosine, guanine, 2′-deoxyguanosine, guanosine,0-methylguanine, methylguanine, caffeine, xanthine, theophylline,theobromine, adenine, adenosine, 2′-deoxyadenosine,N-benzyl-9-(2-tetrahydropyranyl)adenine, and adenosine triphosphate.They may be used alone or as a mixture of two or more.

If necessary, the ink composition according to the present invention mayfurther contain assistants commonly used in ink for ink jet recording.Examples of assistants usable herein include penetrants, viscositymodifiers, surface tension modifiers, hydrotropy agents, humectants, pHadjustors, antimolds, chelating agents, preservatives, and rustpreventives.

Penetrants usable herein include: lower alcohols, such as ethanol,isopropanol, butanol, and pentanol; cellosolves, such as ethylene glycolmonobutyl ether; carbitols, such as diethylene glycol monobutyl etherand triethylene glycol monobutyl ether; and surfactants.

Surface tension modifiers usable herein include: alcohols, such asdiethanolamine, triethanolamine, glycerin, and diethylene glycol; andnonionic, cationic, anionic, or amphoteric surfactants.

Preferred hydrotropy agents usable herein include urea, alkylureas,ethyleneurea, propyleneurea, thiourea, guanidine acid salts, andtetraalkylammonium halides.

Regarding the humectant, glycerin, diethylene glycol or the like may beadded as an agent which serves also as the water-soluble organicsolvent. Further, saccharides, such as maltitol, sorbitol, gluconiclactone, and maltose, may be added.

Regarding the pH adjustor, the basic material described above may beadded as a pH adjustor which serves also as the basic material.

According to a preferred embodiment of the present invention, the inkcomposition according to the present invention may contain awater-soluble resin other than the waterfastness-imparting agent.Preferred water-soluble resins of this type include nonionicwater-soluble resins, and examples thereof include polyacrylamide,hydroxy esters of polymethacrylic acid, such as polyhydroxyethylmethacrylate, polyvinyl pyrrolidone, polyvinyl alcohol, and polyethyleneglycol. The addition of these water-soluble resins can further stabilizeink compositions.

Ink Jet Recording Method Using Two Liquids

The ink jet recording Method according to the fourth aspect of thepresent invention comprises the step of printing a reaction solution andan ink composition onto a recording medium.

The ink jet recording method according to the present invention canrealize good images by bringing the reaction solution and the inkcomposition into contact with each other. The reason why good images canbe realized is believed as follows. It should be noted that thefollowing mechanism is merely hypothetical and should not be construedas limiting the present invention. It is believed that, upon the contactof the reaction solution with the ink composition, thewaterfastness-imparting agent breaks the state of dissolution and/ordispersion of a colorant, an optional resin emulsion described below,and other ingredients of the ink composition and to agglomerate them.The agglomerate can inhibit the penetration of the colorant into therecording medium and, as a result, images having high color density andfree from significant feathering and significant unevenness of printingcan be realized. Further, in the case of color images, uneven colormixing in boundaries of different colors, i.e., color bleeding, can alsobe advantageously prevented.

The waterfastness-imparting agent is stably dissolved in the reactionsolution. Upon the deposition of the reaction solution together with theink composition onto a recording medium, the waterfastness-impartingagent electrostatically interacts with the colorant contained in the inkcomposition, while this resin interacts also with the recording mediumand can be stably fixed onto the recording medium. The fixation of theresin onto the recording medium permits the colorant, together with theresin, to be fixed onto the recording medium, thus impartingwaterfastness to the image. Further, as a result of the satisfactoryfixation of the colorant onto the recording medium, images having nosignificant feathering and color bleeding can be realized. Further,advantageously, a combination of the reaction solution containing thewaterfastness-imparting agent represented by formula (I) with an inkcomposition containing a dye could have significantly improvedlightfastness. In the prior art, a combination of a polyallylamine usedas a cationic water-soluble resin with a dye was disadvantageous in thatthe lightfastness becomes inferior to that of the dye per se. Bycontrast, according to the present invention, the use of thewaterfastness-imparting agent of formula (I) can realize the retentionof the lightfastness of the dye per se. while maintaining thewaterfastness of images, which is unattainable by the conventionalcombination.

The reaction solution and the ink composition may be applied onto therecording medium in any order. Specifically, suitable methods for thedeposition of the reaction solution and the ink composition include amethod wherein the ink composition is deposited onto the recordingmedium after the deposition of the reaction solution onto the recordingmedium, a method wherein the ink composition is first printed onto therecording medium followed by the deposition of the reaction solutiononto the recording medium, and a method wherein the reaction solutionand the ink composition are mixed together just before or just after theejection.

The deposition of the reaction solution onto the recording medium may becarried out by any of a method wherein the reaction solution isselectively deposited onto only an area where the ink composition isdeposited, and a method wherein the reaction solution is deposited onthe whole area of the recording medium. The former method iscost-effective because the consumption of the reaction solution can beminimized. In this method, the accuracy of the position at which boththe reaction solution and the ink composition are deposited should behigh to some extent. On the other hand, in the latter method, ascompared with the former method, the requirement for the accuracy of theposition where the reaction solution and the ink composition aredeposited is relaxed. In the latter method, a larger amount of thereaction solution should be deposited on the whole area of the recordingmedium. This is disadvantageously likely to cause curling of recordingpaper upon drying. For this reason, the method to be used may bedetermined by taking a combination of the ink composition with thereaction solution into consideration. When the former method is adopted,the reaction solution may be deposited by ink jet recording.

(a) Reaction Solution

The reaction solution used in the ink jet recording method according tothe fourth aspect of the present invention basically comprises thewaterfastness-imparting agent which, upon contact with an inkcomposition, can form an agglomerate. According to the presentinvention, as described above, the reaction solution can break the stateof dispersion and/or dissolution of a dye or a pigment, an optionalresin emulsion, and other ingredients of the ink composition and toagglomerate them.

The amount of the waterfastness-imparting agent added to the reactionsolution may be properly determined so that the above effect can beattained. The waterfastness-imparting agent is added preferably in anamount of about 0.2 to 20% by weight, more preferably about 0.5 to 10%by weight, based on the reaction solution.

According to a preferred embodiment of the present invention, thereaction solution contains an acidic material. Acidic materials usableherein include, for example, inorganic acids, such as hydrochloric acid,bromic acid, hydrofluoric acid, sulfuric acid, phosphoric acid, andnitric acid, and organic acids, such as acetic acid, propionic acid,n-butyric acid, iso-butyric acid, n-valeric acid, glycolic acid,gluconic acid, lactic acid, and toluenesulfonic acid.

According to a preferred embodiment of the present invention, thereaction solution further contains a basic material. Examples of basicmaterials usable herein include: inorganic bases, such as sodiumhydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide,barium hydroxide, strontium hydroxide, radium hydroxide, beryliumhydroxide, magnesium hydroxide, and ammonia; mono-, di- or tri-loweralkylamines, such as ethylamine, diethylamine, triethylamine,propylamine, dipropylamine, diisopropylamine, tert-butylamine,dibutylamine, diisobutylamine, isopropylamine, sec-butylamine, andpentylamine; lower alkyl lower hydroxyalkoxyamines, such as3-ethoxypropylamine and 3-methoxypropylamine; lower alkyl loweralkoxyamines, such as 3-ethoxypropylamine and 3-methoxypropylamine;mono-, di- or tri-lower hydroxyalkylamines, such as 2-aminoethanol,2-(dimethylamino)ethanol, 2-(diethylamino)ethanol, diethanolamine,N-butyldiethanolamine, triethanolamine, aminomethylpropanol, andtriisopropanolamine; and organic amines, such as iminobispropylamine,3-diethylaminopropylamine, dibutylaminopropylamine,methylaminopropylamine, dimethylaminopropanediamine, andmethyliminobispropylamine.

According to a preferred embodiment of the present invention, thereaction solution of the present invention contains a water-solubleresin other than the waterfastness-imparting agent. Preferredwater-soluble resins of this type include nonionic water-soluble resins,and examples thereof include polyacrylamide, hydroxy esters ofpolymethacrylic acid, such as polyhydroxyethyl methacrylate, polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol. The addition ofthese water-soluble resins can further stabilize the reaction solution.

The reaction solution used in the ink jet recording method according tothe present invention may contain a polyvalent metal salt. A preferredexample of the polyvalent metal salt usable in the reaction solution isa salt that is constituted by divalent or higher polyvalent metal ionsand anions bonded to the polyvalent metal ions and is soluble in water.Specific examples of polyvalent metal ions include divalent metal ions,such as Ca²⁺, Cu²⁺, Ni²⁺, Mg²⁺, Zn²⁺, and Ba²+, trivalent metal ions,such as A³⁺, Fe³⁺, and Cr³⁺. Anions include Cl⁻, NO₃ ⁻, I⁻, Br⁻, ClO₃ ⁻,and CH₃COO⁻.

Among them, a metal salt constituted by Ca²⁺ or Mg²⁺ provides favorableresults in terms of pH of the reaction solution and the quality ofprints.

The concentration of the polyvalent metal salt in the reaction solutionmay be suitably determined so as to attain the effect of providing goodprint quality and preventing clogging. It, however, is preferably about0.1 to 40% by weight, more preferably about 5 to 25% by. weight.

According to a preferred embodiment of the present invention, thepolyvalent metal salt contained in the reaction solution is constitutedby divalent or higher polyvalent metal ions and nitrate ions orcarboxylate ions bonded to the polyvalent metal ions and is soluble inwater.

In this case, preferably, the carboxylate ions are derived from asaturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms or acarbocyclic monocarboxylic acid having 7 to 11 carbon atoms. Preferredexamples of the saturated aliphatic monocarboxylic acid having 1 to 6carbon atoms include formic acid, acetic acid, propionic acid, butyricacid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, andhexanoic acid. Among them, formic acid and acetic acid are particularlypreferred.

A hydrogen atom(s) on the saturated aliphatic hydrocarbon group in themonocarboxylic acid may be substituted by a hydroxyl group. Preferredexamples of such carboxylic acids include lactic acid.

Preferred examples of the carbocyclic monocarboxylic acid having 6 to 10carbon atoms include benzoic acid and naphthoic acid with benzoic acidbeing more preferred.

According to a preferred embodiment of the present invention, thereaction solution may contain a wetting agent comprising a high-boilingorganic solvent. The high-boiling organic solvent functions to preventthe reaction solution from drying out, thereby preventing clogging ofthe head. Preferred examples of high-boiling organic solvents usableherein include: polyhydric alcohols, such as ethylene glycol, diethyleneglycol, triethylene glycol, polyethylene glycol, polypropylene glycol,propylene glycol, butylene glycol, 1,2,6-hexanetriol, thiodiglycol,hexylene glycol, glycerin, trimethylolethane, and trimethylolpropane;alkyl ethers of polyhydric alcohols, such as ethylene glycol monoethylether, ethylene glycol monobutyl ether, diethylene glycol monomethylether, diethylene glycol monoethyl ether, diethylene glycol monobutylether, triethylene glycol monomethyl ether, triethylene glycol monoethylether, and triethylene glycol monobutyl ether; urea; 2-pyrrolidone;N-methyl-2-pyrrolidone; 1,3-dimethyl-2-imidazolidinone; andtriethanolamine.

Although the amount of the high-boiling organic solvent added is notparticularly limited, it is preferably about 0.5 to 40% by weight, morepreferably about 2 to 20% by weight.

According to a preferred embodiment of the present invention, thereaction solution may further contain a low-boiling organic solvent.Examples of preferred low-boiling organic solvents usable herein includemethanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol,sec-butanol, tert-butanol, iso-butanol, and n-pentanol. Monohydricalcohols are particularly preferred. The low-boiling organic solvent hasthe effect of shortening the time required for drying the reactionsolution on the recording medium. The low-boiling organic solvent isadded preferably in an amount of 0.5 to 10% by weight, more preferably1.5 to 6% by weight.

According to a preferred embodiment of the present invention, thereaction solution may further contain a penetrant. Penetrants usableherein include various surfactants, such as anionic, cationic,amphoteric, and nonionic surfactants; alcohols, such as methanol,ethanol, and iso-propyl alcohol; and lower alkyl ethers of polyhydricalcohols, such as ethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, diethylene glycol monobutyl ether, triethylene glycolmonobutyl ether, propylene glycol monobutyl ether, and dipropyleneglycol monobutyl ether.

(b) Ink Composition

The ink composition used in the ink jet recording method according tothe fourth aspect of the present invention refers to a black inkcomposition in the case of monochrome printing and color inkcompositions in the case of color printing, specifically yellow,magenta, and cyan ink compositions, and optionally a black inkcomposition.

The ink composition used in the present invention comprises at least acolorant and water.

The colorant contained in the ink composition used in the presentinvention may be either a dye or a pigment.

Dyes are organic color materials, soluble in water, and preferred dyesare those that fall into categories of acidic dyes, direct dyes,reactive dyes, soluble vat dyes, and food dyes according to the colorindex. Further, colorants, insoluble in neutral water, falling withincategories of oil-soluble dyes, basic dyes, or pigments according to thecolor index may also be used so far as they are soluble in aqueousalkali solutions.

Specific examples of dyes and alkali-soluble pigments include thosedescribed above in connection with the ink composition according to thesecond aspect of the present invention.

Regarding the pigment, inorganic and organic pigments are usable withoutparticular limitation. Examples of inorganic pigments usable hereininclude, in addition to titanium oxide and iron oxide, carbon blacksproduced by known processes, such as contact, furnace, and thermalprocesses. Examples of organic pigments usable herein include azopigments (including azo lake, insoluble azo pigment, condensed azopigment, and chelate azo pigment), polycyclic pigments (for example,phthalocyanine, perylene, perinone, anthraquinone, quinacridone,dioxazine, thioindigo, isoindolinone, and quinophthalone pigments),dye-type chelate pigment (for example, basic dye-type chelate pigmentsand acid dye-type chelate pigment), nitro pigments, nitroso pigments,and aniline black. The content of the colorant may be properlydetermined. For example, the content of the colorant is preferably 0.5to 20% by weight based on the total weight of the ink composition. Thisis because a colorant content falling within the above range can provideprinted images having satisfactory optical density and permits theviscosity of the ink to be easily adjusted to a value suitable for inkjet recording.

According to a preferred embodiment of the present invention, pigmentsamong these colorants are brought to a form dispersible in an aqueousmedium with the aid of a dispersant or a surfactant or by surfacetreatment to introduce an anionic functional group thereinto. Thispermits pigment particles to be stably dispersed in the ink composition.On the other hand, the waterfastness-imparting agent contained in thereaction solution can electrostatically interact with the introducedfunctional group on recording media to realize sharp images having nosignificant feathering or color bleeding.

According to a preferred embodiment of the present invention, the inkcomposition may contain a resin emulsion. The term “resin emulsion” usedherein refers to an emulsion comprising water as a continuous phase andthe following resin component as a dispersed phase. Resin components asthe dispersed phase include acrylic resin, vinyl acetate resin,styrene/butadiene resin, vinyl chloride resin, (meth)acrylate/styreneresin, butadiene resin, styrene resin, crosslinked acrylic resin,crosslinked styrene resin, benzoguanamine resin, phenolic resin,silicone resin, and epoxy resin.

According to a preferred embodiment of the present invention, the resinis a polymer having a combination of a hydrophilic segment with ahydrophobic segment. The particle diameter of the resin component is notparticularly limited so far as the resin component can form an emulsion.It, however, is preferably not more than about 150 nm, more preferablyabout 5 to 100 nm.

The resin emulsion may be prepared by dispersion polymerization of resinmonomer, optionally together with a surfactant, in water. For example,an emulsion of an acrylic resin or a styrene/(meth)acrylic resin may beprepared by dispersion polymerization of an ester of (meth)acrylic acidor alternatively styrene in combination with an ester of (meth)acrylicacid in water in the presence of a surfactant. In general, the mixingratio of the resin component to the surfactant is preferably about 10:1to 5:1.

When the amount of the surfactant used is in the above amount range,better waterfastness and penetration of ink can be attained. Thesurfactant is not particularly limited. Preferred examples thereofinclude: anionic surfactants (for example, sodiumdodecylbenzenesulfonate, sodium laurylate, and an ammonium salt ofpolyoxyethylene alkyl ether sulfates), nonionic surfactants (forexample, polyoxyethylene alkyl ethers, polyoxyethylene alkyl esters,polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenylethers, polyoxyethylenealkylamines, and polyoxyethylenealkylamides).They may be used alone or in combination of two or more. Further,acetylene glycols, for example, Olfine Y, Surfynol 82, Surfynol 104,Surfynol 440, Surfynol 465, and Surfynol 485 (all the above productsbeing manufactured by Air Products and Chemicals Inc.) may also be used.

Further, commercially available resin emulsions may also be used, andexamples thereof include Microgel E-1002 and E-5002 (emulsion ofstyrene/acrylic resin, manufactured by Nippon Paint Co., Ltd.), Voncoat4001 (emulsion of acrylic resin, manufactured by Dainippon Ink andChemicals, Inc.), Voncoat 5454 (emulsion of styrene/acrylic resin,manufactured by Dainippon Ink and Chemicals, Inc.), SAE-1014 (emulsionof styrene/acrylic resin, manufactured by Nippon Zeon Co., Ltd.), andSaivinol SK-200 (emulsion of acrylic resin, manufactured by SaidenChemical Industry Co., Ltd).

The content of the resin emulsion in the ink composition used in thepresent invention is preferably 0.1 to 40% by weight, more preferably 1to 25% by weight, in terms of resin component.

The resin emulsion, by virtue of interaction with thewaterfastness-imparting agent, can inhibit the penetration of thecolorant component and, in addition, has the effect of accelerating thefixation of the colorant component onto a recording medium. Further,some resin emulsions has also the effect of forming a film on therecording medium to improve the rubbing/scratch resistant of prints.

According to a preferred embodiment of the present invention, the inkcomposition contains a thermoplastic resin in a resin emulsion form. Thethermoplastic resin has a softening temperature of 50 to 250° C.,preferably 60 to 200° C. Regarding the thermoplastic resin, the term“softening temperature” used herein refers to the lowest temperatureamong the glass transition point, the melting point, the temperaturenecessary for providing a viscosity coefficient of 10¹¹ to 10¹² poises,the fluidized point, and, in the case of a resin emulsion form, theminimum film-forming temperature (MFT) of thermoplastic resin. In thestep of heating in the method according to the present invention, therecording medium is heated at a temperature of the softening temperatureof the thermoplastic resin or above.

Further, preferably, the thermoplastic resin forms a strong film havingwaterfastness and rubbing/scratch resistance, when heated at thesoftening or melting temperature or a higher temperature and thencooled.

Specific examples of water-insoluble thermoplastic resins include, butare not limited to, polyacrylic acid, polymethacrylic acid, apolymethacrylic ester, polyethylacrylic acid, a styrene/butadienecopolymer, polybutadiene, an acrylonitrile/butadiene copolymer, achloroprene copolymer, a fluororesin, polyvinylidene fluoride,polyolefin resin, cellulose, a styrene/acrylic acid copolymer, astyrene/methacrylic acid copolymer, polystyrene, a styrene/acrylamidecopolymer, polyisobutyl acrylate, polyacrylonitrile, polyvinyl acetate,polyvinyl acetal, polyamide, rosin resin, polyethylene, a polycarbonate,a vinylidene chloride resin, a cellulosic resin, a vinyl acetate resin,an ethylene/vinyl acetate copolymer, a vinyl acetate/(meth)acrylatecopolymer, a vinyl chloride resin, polyurethane, and a rosin ester.

Specific examples. of low-molecular weight thermoplastic resins includepolyethylene wax, montan wax, alcohol wax, synthetic oxide wax, anα-olefin/maleic anhydride copolymer, animal and vegetable waxes such ascarnauba wax, lanolin, paraffin wax, and microcrystalline wax.

Conventional resin emulsions may also be used as the resin emulsion. Forexample, resin emulsions described in Japanese Patent Publication No.1426/1987 and Japanese Patent Laid-Open Nos. 56573/1991, 79678/1991,160068/1991, and 18462/1992 as such may be used.

According to a preferred embodiment of the present invention, the inkcomposition contains an alginic acid derivative. Examples of preferredalginic acid derivatives include alkali metal alginates (for example,sodium salt and potassium salt), organic salts of alginic acid (forexample, triethanolamine salt), and ammonium alginate.

The alginic acid derivative is added to the ink composition preferablyin an amount of about 0.01 to 1% by weight, more preferably about 0.05to 0.5% by weight.

The reason why the addition of the alginic acid derivative can realizegood images has not been fully elucidated yet. The reason is howeverbelieved that a waterfastness-imparting agent in the reaction solutionreacts with the alginic acid derivative contained in the ink compositionto change the state of dissolution or dispersion of the colorant andconsequently to accelerate the fixation of the colorant onto therecording medium.

According to a preferred embodiment of the present invention, the inkcomposition contains an organic solvent. The organic solvent ispreferably a low-boiling organic solvent. Preferred examples thereofinclude methanol, ethanol, n-propyl alcohol, isopropyl alcohol,n-butanol, sec-butanol, tert-butanol, isobutanol, and n-pentanol.Monohydric alcohols are particularly preferred. The low-boiling organicsolvent has the effect of shortening the drying time of the ink.

According to a preferred embodiment of the present invention, the inkcomposition used in the ink jet recording method according to the fourthaspect of the present invention further contains a wetting agentcomprising a high-boiling organic solvent. Preferred examples ofhigh-boiling organic solvents include: polyhydric alcohols, such asethylene glycol, diethylene glycol, triethylene glycol, polyethyleneglycol, polypropylene glycol, propylene glycol, butylene glycol,1,2,6-hexanetriol, thioglycol, hexylene glycol, glycerin,trimethylolethane, and trimethylolpropane; alkyl ethers of polyhydricalcohols, such as ethylene glycol monoethyl ether, ethylene glycolmonobutyl ether, diethylene glycol monomethyl ether, diethylene glycolmonoethyl ether, diethylene glycol monobutyl ether, triethylene glycolmonomethyl ether, triethylene glycol monoethyl ether, and triethyleneglycol monobutyl ether; urea; 2-pyrrolidone; N-methyl-2-pyrrolidone;1,3-dimethyl-2-imidazolidinone; and triethanolamine.

The wetting agent is added preferably in an amount of 0.5 to 40% byweight, more preferably 2 to 20% by weight, based on the ink. Thelow-boiling organic solvent is added preferably in an amount of 0.5 to10% by weight, more preferably 1.5 to 6% by weight, based on the ink.

The ink composition used in the present invention may contain adispersant and a surfactant. Examples of surfactants usable hereininclude various surfactants described above in connection with the resinemulsion.

According to a preferred embodiment of the present invention, the inkcomposition contains a saccharide. Examples of saccharides usable hereininclude monosaccharides, disaccharides, oligosaccharides (includingtrisaccharides and tetrasaccharides), and other polysaccharides,preferably glucose, mannose, fructose, ribose, xylose, arabinose,galactose, aldonic acid, glucitol, sorbitol, maltose, cellobiose,lactose, sucrose, trehalose, and maltotriose. The term “polysaccharide”used herein means saccharides in the broad sense as including substanceswhich exist widely in the world of nature, such as alginic acid,α-cyclodextrin, and cellulose.

Derivatives of these saccharides usable herein include reducing sugarsof the above saccharides (for example, sugar alcohols represented by thegeneral formula HOCH₂(CHOH)_(n)CH₂OH, wherein n is an integer of 2 to5), oxidizing sugars (for example, aldonic acid or uronic acid), aminoacids, and thiosugars. Among them, sugar alcohols are particularlypreferred, and specific examples thereof include maltitol and sorbitol.

The saccharide is added suitably in an amount of 0.1 to 40% by weight,preferably 0.5 to 30% by weight, based on the ink composition.

If necessary, pH adjustors, preservatives, antimolds and the like may beadded to the ink composition used in the present invention.

According to a preferred embodiment of the present invention, the inkcomposition according to the second embodiment of the present inventionmay be used as the ink composition in the ink jet recording methodaccording to the fourth embodiment of the present invention. This canyield high-quality images having excellent waterfastness andlightfastness and a lower level of feathering or bleeding.

(c) Ink Jet Recording Apparatus

An ink jet recording apparatus usable in practicing the ink jetrecording method according to the fourth embodiment of the presentinvention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of an ink jet. recording apparatus. In thisembodiment, an ink composition and a reaction solution are accommodatedin a tank and fed into a recording head through an ink tube.Specifically, a recording head 1 is communicated with an ink tank 2through an ink tube 3. In this case, the interior of the ink tank 2 ispartitioned, and a chamber for an ink composition, optionally aplurality of chambers respectively for a plurality of color inkcompositions, and a chamber for a reaction solution are provided.

The recording head 1 is moved along a carriage 4 by means of a timingbelt 6 driven by a motor 5. On the other hand, paper 7 as a recordingmedium is placed by a platen 8 and a guide 9 at a position facing therecording head 1. In this embodiment, a cap 10 is provided. A suctionpump 11 is connected to the cap 10 in order to conduct the so-called“cleaning operation.” The ink composition sucked by the suction pump 11is resorvoired in a waste ink tank 13 through a tube 12.

FIG. 2 is an enlarged view showing the surface of nozzles for therecording head 1. In the drawing, the surface of a nozzle for a reactionsolution is indicated by 1 b, and a nozzle 21 for ejecting the reactionsolution is provided in the longitudinal direction. On the other hand,the surface of nozzles for the ink composition is indicated by 1 c, anda yellow ink composition, a magenta ink composition, a cyan inkcomposition, and a black ink composition are ejected respectivelythrough nozzles 22, 23, 24 and 25.

Further, an ink jet recording method using the recording head shown inFIG. 2 will be described with reference to FIG. 3. The recording head 1is moved in the direction indicated by an arrow A, during which time thereaction solution is ejected through the nozzle surface 1 b to form areaction solution-deposited region 31 in a band form on the recordingmedium 7. Subsequently, the recording medium 7 is transferred by apredetermined extent in the paper feed direction indicated by an arrowB, during which time the recording head 1 is moved in the directionopposite to that indicated by the arrow A in the drawing and returned tothe left end of the recording medium 7, and the recording head 1conducts printing using the ink composition on the reactionsolution-deposited region, thereby forming a print region 32.

Further, as shown in FIG. 4, in the recording head 1, it is alsopossible to arrange all nozzles in the lateral direction to construct anozzle assembly. In the drawing, ejection nozzles for a reactionsolution are denoted by 41 a and 41 b, and a yellow ink composition, amagenta ink composition, a cyan ink composition, and a black inkcomposition are ejected respectively through nozzles 42, 43, 44 and 45.In the recording head according to this embodiment, the recording head1, when reciprocated on the carriage, can conduct printing in bothdirections. Therefore, in this case, printing at a higher speed isexpected as compared with the case where the recording head shown inFIG. 2 is used.

Regulating the surface tension of the reaction solution and the inkcomposition preferably by the above method enables a high-quality printto be more stably provided independently of the order of depositing thereaction solution and the ink composition. In this case, use of only oneejection nozzle for the reaction solution suffices for desired results(for example, the nozzle indicated by numeral 41 b in the drawing may beomitted), leading to a further reduction in size of head and an increasein printing speed.

In the ink jet recording apparatus, the supplement of the inkcomposition may be carried out by replacing a cartridge as an ink tank.The ink tank may be integral with the recording head.

A preferred embodiment of an ink jet recording apparatus using such anink tank is shown in FIG. 5. In the drawing, the same members as used inthe apparatus shown in FIG. 1 have the same reference numerals. In theembodiment shown in FIG. 5, recording heads 1 a and 1 b are integralrespectively with ink tanks 2 a and 2 b. An ink composition and areaction solution are ejected respectively through the recording heads 1a and 1 b. Basically, printing may be conducted in the same manner asdescribed above in connection with the apparatus shown in FIG. 1.Further, in this embodiment, the recording head la is moved togetherwith the ink tank 2 a on a carriage 4, while the recording head 1 a ismoved together with the ink tank 2 b on the carriage 4.

EXAMPLES

The present invention will be described in more detail with reference tothe following examples, though go it is not limited to these examplesonly.

Example A Preparation A1 Preparation of Waterfastness-imparting Agent A1

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 15.0g of N,N-dimethylaminopropylacrylamide, 0.57 g of2,4-diphenyl-4-methyl-1-pentene, and 20.0 g of n-butyl acetate. Asolution of 0.44 g of dimethyl 2,2′-azobis(2-methyl propionate)dissolved in 20.0 g of n-butyl acetate was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionmixture was then heated to 95 ° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 56 g of a pale yellow transparent solution. The solvent wasremoved under the reduced pressure. A highly viscous liquid as theresidue was dissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 13.0 g of asolid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 10.0g of water and 5.0 g of the solid prepared above. The reaction mixturewas heated while stirring under a nitrogen atmosphere, and the solutionwas then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 15 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 4.8 g of asolid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 9,400 and5,100 respectively, against polyethylene glycol standards.

Preparation A2 Preparation of Waterfastness-imparting Agent A2

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 14.0g of N,N-dimethylaminopropylacrylamide, 1.3 g of a 75 wt % aqueoussolution of (3-acrylamidopropyl)trimethylammonium chloride, 0.90 g of2,4-diphenyl-4-methyl-1-pentene, and 20.0 g of N,N-dimethylformamide. Asolution of 1.09 g of dimethyl 2,2′-azobis(2-methyl propionate)dissolved in 20.0 g of N,N-dimethylformamide was then added to theflask. The reaction mixture was heated to 80° C. while stirring under anitrogen atmosphere, and the solution was kept at 80° C. for 4 hr. Thereaction mixture was then heated to 95° C., and the reaction wascontinued for additional 2 hr at 95° C., followed by cooling to roomtemperature to give about 57 g of a pale yellow transparent solution.The solvent was removed under the reduced pressure. A highly viscousliquid as the residue was dissolved in methyl ethyl ketone, and aprecipitation procedure from a mixture of methyl ethyl ketone and hexanewas repeated several times. The resulting precipitate was dried to give12.3 g of a solid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 30 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 9.6 g of asolid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 4,200 and2,800, respectively, against polyethylene glycol standards.

Preparation A3 Preparation of Waterfastness-imparting Agent A3

A 500-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 52.6g of N,N-dimethylaminopropylacrylamide, 23.2 g of a 75 wt % aqueoussolution of (3-acrylamidopropyl)trimethylammonium chloride, 4.0 g of2,4-diphenyl-4-methyl-1-pentene, and 130 g of N,N-dimethylformamide. Asolution of 5.0 g of dimethyl 2,2′-azobis(2-methyl propionate) dissolvedin 20 g of N,N-dimethylformamide was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionsolution was then heated to 95° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 230 g of a pale yellow transparent solution. The solvent wasremoved under the reduced pressure. A highly viscous liquid as theresidue was dissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 40.3 g of asolid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 30 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 9.2 g of asolid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 4,800 and3,200, respectively, against polyethylene glycol standards.

Preparation A4 Preparation of Waterfastness-imparting Agent A4

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 15.0g of N,N-dimethylaminopropylacrylamide, 0.57 g of2,4-diphenyl-4-methyl-1-pentene, and 20.0 g of methanol. A solution of0.54 g of 4,4′-azobis(4-cyanopentanoic acid) dissolved in 20.0 g ofmethanol was then added to the flask. The reaction mixture was heatedwhile stirring under a nitrogen atmosphere, and a reaction was allowedto proceed at the boiling point for 15 hr. The reaction mixture was thencooled to room temperature to give about 50 g of a pale yellowtransparent solution. The solvent was removed under the reducedpressure. A highly viscous liquid as the residue was dissolved in methylethyl ketone, and a precipitation procedure from a mixture of methylethyl ketone and hexane was repeated several times. The resultingprecipitate was dried to give 13.0 g of a solid. The weight-averagemolecular weight and the number-average molecular weight of the polymerwere determined by GPC to be 8,900 and 4,700, respectively, againstpolyethylene glycol standards.

Preparation A5 Preparation of waterfastness-imparting agent A5

A 200-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 15.0g of N,N-dimethylaminopropylacrylamide, 0.50 g of 3-mercaptopropionicacid, and 60.0 g of n-butyl acetate. Thereafter, 2.00 g of1,1′-azobis(1-acetoxy-1-phenylethane) was introduced into the solutionfollowed by dissolution with stirring. The reaction mixture was heatedto 80° C. while stirring under a nitrogen atmosphere, and the solutionwas kept at 80° C. for 4 hr. The reaction solution was then heated to95° C., and the reaction was continued for additional 2 hr at 95° C.,followed by cooling to room temperature to give about 77 g of a paleyellow solution. The solvent was removed under the reduced pressure. Ahighly viscous liquid as the residue was dissolved in acetone, and aprecipitation procedure from a mixture of acetone and hexane wasrepeated several times. The resulting precipitate was dried to give 13.5g of a solid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 6,000 and2,200, respectively, against polyethylene glycol standards.

Preparation A6 Preparation of waterfastness-imparting agent A6

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 12.5g of N,N-dimethylaminoethylacrylamide, 0.83 g of2,4-diphenyl-4-methyl-1-pentene, and 20.0 g of n-butyl acetate. Asolution of 0.41 g of dimethyl 2,2′-azobis(2-methyl propionate)dissolved in 20.0 g of n-butyl acetate was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionsolution was then heated to 95° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 56 g of a pale yellow transparent solution. The solvent wasremoved under the reduced pressure. A highly viscous liquid as theresidue was dissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 12.0 g of asolid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 30 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 9.0 g of asolid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 6,700 and3,800, respectively, against polyethylene glycol standards.

Preparation A7 Preparation of waterfastness-imparting agent A7

A reaction and purification were carried out in the same manner as inPreparation Al, except that the amount of2,4-diphenyl-4-methyl-1-pentene added was changed to 1.13 g. The yieldof the product after drying was 4.5 g. The weight-average molecularweight and the number-average molecular weight of the polymer weredetermined by GPC to be 4,600 and 2,700, respectively, againstpolyethylene glycol standards.

Preparation A8 Preparation of Waterfastness-imparting Agent A8

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 15.0g of N,N-dimethylaminopropylmethacrylamide, 0.83 g of2,4-diphenyl-4-methyl-1-pentene, and 20.0 g of n-butyl acetate. Asolution of 0.41 g of dimethyl 2,2′-azobis(2-methyl propionate)dissolved in 20.0 g of n-butyl acetate was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionsolution was then heated to 95° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 56 g of a pale yellow transparent solution. The solvent wasremoved under the reduced pressure. A highly viscous liquid as theresidue was dissolved in acetone, and a precipitation procedure from amixture of acetone and hexane was repeated several times. The resultingprecipitate was dried to give 12.9 g of a solid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 31 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in acetone, and a precipitation procedure from amixture of acetone and hexane was repeated several times. The resultingprecipitate was dried to give 9.4 g of a solid. The weight-averagemolecular weight and the number-average molecular weight of the polymerwere determined by GPC to be 7,000 and 4,000, respectively, againstpolyethylene glycol standards.

Preparation A9 Preparation of Waterfastness-imparting Agent A9

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a ref lux condenser was charged with 5.0g of the product prepared in Preparation A1, and this product in theflask was dissolved in 10.0 g of methyl ethyl ketone and 10.0 g ofmethanol. Methyl iodide (0.22 g) was gradually added to the solutionwhile stirring the solution. The solution was then heated to 60° C., anda reaction was allowed to proceed at 60° C. for 8 hr. The reactionsolution was then cooled to room temperature to give about 24 g of apale yellow transparent solution. The solvent was removed under thereduced pressure. The residue was redissolved in methanol, and aprecipitation procedure from a mixture of methanol and acetone wasrepeated several times. The resulting precipitate was dried to give 3.5g of a solid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 8,600 and5,300, respectively, against polyethylene glycol standards.

Example A1 Preparation of Ink Set A1

To 2.0 g of the waterfastness-imparting agent A1 prepared in PreparationA1 were added 4 g of C.I. Acid Black 24, 11 g of glycerin, 5 g of2-pyrrolidinone, and 10 g of diethylene glycol monobutyl ether. Further,ultrapure water was added to bring the total amount of the mixture to100 g. Thus, a black ink A1 was prepared.

Yellow ink A1, magenta ink A1, and cyan ink A1 were prepared in the samemanner as above, except that the dye was changed to 3 g of C.I. AcidYellow 23 for the yellow ink A1, 2 g of C.I. Acid Red 13 for the magentaink A1, and 2.5 g of C.I. Acid Blue 9 for the cyan ink A1.

These four inks were combined to give ink set A1.

Example A2 Preparation of Ink Set A2

To 3.0 g of the waterfastness-imparting agent A2 prepared in PreparationA2 were added 3.5 g of C.I. Acid Black 1, 12 g of diethylene glycol, 5 gof 1,3-dimethyl-2-imidazolidinone, 5 g of urea, 7 g of triethyleneglycol monobutyl ether, and 0.1 g of potassium hydroxide. Further,ultrapure water was added to bring the total amount of the mixture to100 g. Thus, a black ink A2 was prepared.

Yellow ink A2, magenta ink A2, and cyan ink A2 were prepared in the samemanner as above, except that the dye was changed to 3.0 g of C.I. AcidYellow 17 for the yellow ink A2, 2.5 g of C.I. Acid Red 1 for themagenta ink A2, and 4.0 g of C.I. Direct Blue 86 for the cyan ink A2.

These four inks were combined to give ink set A2.

Example A3 Preparation of Ink Set A3

To 2.0 g of the waterfastness-imparting agent A3 prepared in PreparationA3 were added 4.5 g of C.I. Direct Black 32, 9 g of glycerin, 5 g ofthiodiglycol, 5 g of diethylene glycol monobutyl ether, 10 g ofN-methylimidazole, 0.9 g of triethanolamine, 0.2 g of sodium hydroxide,and 1 g of Surfynol 465 (tradename; manufactured by Air Products andChemicals Inc.). Further, ultrapure water was added to bring the totalamount of the mixture to 100 g. Thus, a black ink A3 was prepared.

Yellow ink A3, magenta ink A3, and cyan ink A3 were prepared in the samemanner as above, except that the dye was changed to 2 g of Daiwa IJYellow 214 HL (tradename; C.I. Direct Yellow 86, manufactured by DaiwaDye Stuff Mfg. Co., Ltd.) for the yellow ink A3, 6 g of Palatine FastPink BN 1 for the magenta ink A3, and 3.5 g of C.I. Direct Blue 199 forthe cyan ink A3.

These four inks were combined to give an ink set A3.

Example A4 Preparation of Ink Set A4

To 1.8 g of the waterfastness-imparting agent A4 prepared in PreparationA4 were added 4.5 g of C.I. Direct Black 32, 9 g of glycerin, 5 g oftriethylene glycol, 5 g of maltitol, 3 g of L-histidine, 0.6 g oftriethanolamine, 2.5 g of ethanol, and 1 g of Surfynol 465 (tradename;manufactured by Air Products and Chemicals Inc.). Further, ultrapurewater was added to bring the total amount of the mixture to 100 g. Thus,a black ink A4 was prepared.

Yellow ink A4, magenta ink A4, and cyan ink A4 were prepared in the samemanner as above, except that the dye was changed to 2 g of Daiwa IJYellow 214 HL (tradename; C.I. Direct Yellow 86, manufactured by DaiwaDye Stuff Mfg. Co., Ltd.) for the yellow ink A4, 6 g of Palatine FastPink BNI for the magenta ink A4, and 3.5 g of C.I. Direct Blue 199 forthe cyan ink A4.

These four inks were combined to give an ink set A4.

Example A5 Preparation of Ink Set A5

C.I. Direct Black 19 (6 g) was dissolved in 2.7 g of thewaterfastness-imparting agent A5 prepared in Preparation A5.Thiodiglycol (10 g) and 10 g of diethylene glycol monoethyl ether wereadded to the solution. Further, ultrapure water was added to bring thetotal amount of the mixture to 100 g. Thus, a black ink A5 was prepared.

Yellow ink A5, magenta ink A5, and cyan ink A5 were prepared in the samemanner as above, except that the dye was changed to 3.2 g of MY 123(tradename; manufactured by Arimoto Chemical Company Ltd.) for theyellow ink A5, 3.2 g of Savinyl Pink 6 BLS (tradename; manufactured byClariant Japan K.K.) for the magenta ink A5, and 3 g of Valifast Blue1605 for the cyan ink A5.

These four inks were combined to give an ink set A5.

Example A6 Preparation of Ink Set A6

The waterfastness-imparting agent A6 (3.2 g) prepared in Preparation A6was mixed with 6 g of C.I. Food Black 2, 12 g of glycerin, 10 g oftriethylene glycol monobutyl ether, 5 g of diethylene glycol, 3.0 g ofguanidine, and 1.2 g of a nonionic surfactant Surfynol 465. Further,ultrapure water was added to bring the total amount of the mixture to100 g. Thus, a black ink A6 was prepared.

Yellow ink A6, magenta ink A6, and cyan ink A6 were prepared in the samemanner as above, except that the dye was changed to 5 g of C.I. AcidYellow 23 for the yellow ink A6, 2.5 g of C.I. Acid Red 249 for themagenta ink A6, and 4 g of C.I. Direct Blue 86 for the cyan ink A6.These four inks were combined to give an ink set A6.

Example A7 Preparation of Ink Set A7

To 5.0 g of the waterfastness-imparting agent A7 prepared in PreparationA7 were added 5.0 g of C.I. Acid Black 1, 10 g of glycerin, 5 g of2-pyrrolidinone, and 10 g of triethylene glycol monobutyl ether.Further, ultrapure water was added to bring the total amount of themixture to 100 g. Thus, a black ink A7 was prepared.

Yellow ink A7, magenta ink A7, and cyan ink A7 were prepared in the samemanner as above, except that the dye was changed to 3.0 g of C.I. AcidYellow 17 for the yellow ink A7, 2.5 g of C.I. Acid Red 1 for themagenta ink A7, and 4.0 g of C.I. Direct Blue 86 for the cyan ink A7.These four inks were combined to give an ink set A7.

Example A8 Preparation of Ink Set A8

Black ink A8, yellow ink A8, magenta ink A8, and cyan ink A8 wereprepared in the same manner as in Example A1, except that 2.8 g of thewaterfastness-imparting agent A8 prepared in Preparation A8 was used asthe waterfastness-imparting agent and 5 g of thiourea and 5 g ofdiethylene glycol were additionally used as humectants.

These four inks were combined to give an ink set A8.

Example A9 Preparation of Ink Set A9

Black ink A9, yellow ink A9, magenta ink A9, and cyan ink A9 wereprepared in the same manner as in Example A7, except that 1.0 g of thewaterfastness-imparting agent A1 prepared in Preparation A1 and 2.2 g ofthe waterfastness-imparting agent A7 prepared in Preparation A7 wereused as the waterfastness-imparting agent.

These four inks were combined to give an ink set A9.

Example A10 Preparation of Ink Set A10

Black ink A10, yellow ink A10, magenta ink A10, and cyan ink A10 wereprepared in the same manner as in Example A2, except that 2.7 g of thewaterfastness-imparting agent A9 prepared in Preparation A9 was used asthe waterfastness-imparting agent and 5 g of urea was changed to 5 g of2-(dimethylamino)ethanol.

These four inks were combined to give an ink set A10.

Example A11 Preparation of Ink Set A11

To 3.5 g of the waterfastness-imparting agent A7 prepared in PreparationA7 were added 6 g C.I. Direct Black 195, 12 g of glycerin, 10 g oftriethylene glycol monobutyl ether, 5 g of tetraethylene glycol, 4 g of1,3-dimethyl-2-imidazolidinone, and 1 g of a nonionic surfactantSurfynol 465. Further, ultrapure water was added to bring the totalamount of the mixture to 100 g. Thus, a black ink A11 was prepared.

Yellow ink A11, magenta ink A11, and cyan ink A11 were prepared in thesame manner as above, except that the dye was changed to 5 g of C.I.Acid Yellow 23 for the yellow ink A11, 2.5 g of C.I. Acid Red 249 forthe magenta ink A11, and 4 g of C.I. Direct Blue 86 for the cyan inkA11.

These four inks were combined to give an ink set A1.

Example A12 (Comparative) Preparation of Ink Set A12

Black ink A12, yellow ink A12, magenta ink A12, and cyan ink A12 wereprepared in the same manner as in Example A1, except that thewaterfastness-imparting agent A1 was not used. These four inks werecombined to give an ink set A12.

Example A13 (Comparative) Preparation of Ink Set A13

Black ink A13, yellow ink A13, magenta ink A13, and cyan ink A13 wereprepared in the same manner as in Example A1, except that thewaterfastness-imparting agent A1 was changed to SP-200 (tradename;polyethyleneimine, manufactured by Nippon Shokubai Kagaku Kogyo Co.,Ltd.). These four inks were combined to give a color ink set A13.

Example A14 (Comparative) Preparation of Waterfastness-imparting AgentA10 and Ink Set A14

A 500-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 19.7g of N,N-dimethylaminopropylacrylamide, 81.3 g of a 75 wt % aqueoussolution of (3-acrylamidopropyl)trimethylammonium chloride, 4.0 g of2,4-diphenyl-4-methyl-l-pentene, and 130 g of N,N-dimethylformamide. Asolution of 5.0 g of dimethyl 2,2′-azobis(2-methyl propionate) dissolvedin 20 g of N,N-dimethylformamide was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionsolution was then heated to 95° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 260 g of a pale yellow solution. The solvent was removedunder the reduced pressure. A highly viscous liquid as the residue wasdissolved in methanol, and a precipitation procedure from a mixture ofmethanol and acetone was repeated several times. The resultingprecipitate was dried to give 60.1 g of a solid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 30 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methanol, and a precipitation procedure froma mixture of methanol and acetone was repeated several times. Theresulting precipitate was dried to give 8.1 g of a solid. Theweight-average molecular weight and the number-average molecular weightof the polymer were determined by GPC to be 4,600 and 3,100,respectively, against polyethylene glycol standards.

By the above procedure, a waterfastness-imparting agent A10 having aunit (a) content of 30% by mole was prepared. Black ink A14, yellow inkA14, magenta ink A14, and cyan ink A14 were prepared in the same manneras in Example A3, except that 2.0 g of the waterfastness-imparting agentprepared above was used. These four inks were combined to give an inkset A14.

Evaluation Test on Properties of Ink Compositions

The ink compositions prepared above were evaluated by the followingmethods.

An ink jet recording printer (a color printer MJ-5000C, manufactured bySeiko Epson Corporation) was modified and used in this test. The inkswere filtered through a 5 μm filter before the evaluation test.

Evaluation Test A1 Waterfastness

Acidic plain paper (tradename: Xerox P, manufactured by Fuji Xerox Co.,Ltd.) of size A4 was provided as a recording medium. 1.5 cm-width black,yellow, magenta, and cyan full blotted images and letters were printedat intervals of 3.5 cm (nonrecorded area) on the acidic plain paper. Theprints thus obtained were allowed to stand under natural environment forone hr, and then immersed in 500 ml of water for one hr. After theimmersion, the prints were dried under natural environment for 24 hr.The density of the transfer of the ink onto the nonrecorded area and theresidue of the ink on the recorded area were visually inspected. Theresults were evaluated according to the following criteria.

A: The nonrecorded area was not colored at all, and there was no changein the recorded area.

B: The nonrecorded area was colored for some ink on a level such thatdid not pose any practical problem.

C: There was significant deposition of ink in the nonrecorded area and alowering in color density in the recorded area.

D: Coloration of the nonrecorded area and a lowering in color density inthe recorded area significantly occurred, and, in particular, someletters disappeared and were illegible.

Evaluation Test A2 Lightfastness

The same recording media and printer as used in evaluation test A1 wereused to form full-color images. The prints were evaluated forlightfastness by the whole-day method in the sunlight test according toJIS L 0841. The results were evaluated according to the followingcriteria.

A: A rating change of less than one as compared with the ink with thewaterfastness-imparting agent not added thereto, when evaluation wasdone using a blue scale as a standard.

B: A rating change of one or two.

C: A rating change exceeding three.

Evaluation Test A3 Environmental Stability

A hermetically sealed container containing the ink was allowed to standat 60° C. for one day and then at −30° C. for one day. This procedurewas repeated 10 times. The inks were then visually inspected for theoccurrence of deposits and discoloration. The results were evaluatedaccording to the following criteria.

A: There was no change in the ink.

B: Deposit or discoloration occurred on such a level as will not cause apractical problem.

C: Deposit or discoloration significantly occurred on such a level aswill cause a practical problem.

The evaluation results were as summarized in the following table.

TABLE 1 Environmental Waterfastness Lightfastness stability Example A1 AA A Example A2 A A A Example A3 A A A Example A4 A A A Example A5 A A AExample A6 A A A Example A7 A A A Example A8 A A A Example A9 A A AExample A10 A A A Example A11 A A A Example A12 D A A Example A13 A C AExample A14 A A C

Example B Preparation B1: Preparation of Waterfastness-imparting AgentB1

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 15.0g of N,N-dimethylaminopropylacrylamide, 0.57 g of2,4-diphenyl-4-methyl-1-pentene, and 20.0 g of n-butyl acetate. Asolution of 0.44 g of dimethyl 2,2′-azobis(2-methyl propionate)dissolved in 20.0 g of n-butyl acetate was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionsolution was then heated to 95° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 56 g of a pale yellow transparent solution. The solvent wasremoved under the reduced pressure. A highly viscous liquid as theresidue was dissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 13.0 g of asolid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 10.0g of water and 5.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 15 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 4.8 g of asolid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 9,400 and5,100, respectively, against polyethylene glycol standards.

Preparation B2: Preparation of Waterfastness-imparting Agent B2

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 14.0g of N,N-dimethylaminopropylacrylamide, 1.3 g of a 75 wt % aqueoussolution of (3-acrylamidopropyl)trimethylammonium chloride, 0.90 g of2,4-diphenyl-4-methyl-1-pentene, and 20.0 g of N,N-dimethylformamide. Asolution of 1.09 g of dimethyl 2,2′-azobis(2-methyl propionate)dissolved in 20.0 g of N,N-dimethylformamide was then added to theflask. The reaction mixture was heated to 80° C. while stirring under anitrogen atmosphere, and the solution was kept at 80° C. for 4 hr. Thereaction solution was then heated to 95° C., and the reaction wascontinued for additional 2 hr at 95 ° C., followed by cooling to roomtemperature to give about 57 g of a pale yellow transparent solution.The solvent was removed under the reduced pressure. A highly viscousliquid as the residue was dissolved in methyl ethyl ketone, and aprecipitation procedure from a mixture of methyl ethyl ketone and hexanewas repeated several times. The resulting precipitate was dried to give12.3 g of a solid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 30 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 9.6 g of asolid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 4,200 and2,800, respectively, against polyethylene glycol standards.

Preparation B3: Preparation of Waterfastness-imparting Agent B3

A 500-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 52.6g of N,N-dimethylaminopropylacrylamide, 23.2 g of a 75 wt % aqueoussolution of (3-acrylamidopropyl)trimethylammonium chloride, 4.0 g of2,4-diphenyl-4-methyl-1-pentene, and 130 g of N,N-dimethylformamide. Asolution of 5.0 g of dimethyl 2,2′-azobis(2-methyl propionate) dissolvedin 20 g of N,N-dimethylformamide was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionsolution was then heated to 95° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 230 g of a pale yellow transparent solution. The solvent wasremoved under the reduced pressure. A highly viscous liquid as theresidue was dissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 40.3 g of asolid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thesolution was then kept at 90° C. for 20 hr, followed by cooling to roomtemperature. Thus, about 30 g of a pale yellow transparent solution wasprepared. The solvent was removed under the reduced pressure. Theresidue was redissolved in methyl ethyl ketone, and a precipitationprocedure from a mixture of methyl ethyl ketone and hexane was repeatedseveral times. The resulting precipitate was dried to give 9.2 g of asolid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 4,800 and3,200, respectively, against polyethylene glycol standards.

Preparation B4 Preparation of Waterfastness-imparting Agent B4

A reaction and purification were carried out in the same manner as inPreparation B1, except that the amount of2,4-diphenyl-4-methyl-1-pentene added was changed to 1.13 g. The yieldof the product after drying was 4.5 g. The weight-average molecularweight and the number-average molecular weight of the polymer weredetermined by GPC to be 4,600 and 2,700, respectively, againstpolyethylene glycol standards.

Preparation B5 Preparation of Waterfastness-imparting Agent B5

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 5.0g of the product prepared in Preparation Bi, and this product in theflask was dissolved in 10.0 g of methyl ethyl ketone and 10.0 g ofmethanol. Methyl iodide (1.82 g) was gradually added to the solutionwhile stirring the solution. After the completion of the addition ofmethyl iodide, the solution was heated to 60° C., and a reaction wasallowed to proceed at 60° C. for 8 hr. The reaction mixture was thencooled to room temperature to give about 26 g of a pale yellowtransparent solution. The solvent was removed under the reducedpressure. The residue was redissolved in methanol, and a precipitationprocedure from a mixture of methanol and acetone was repeated severaltimes. The resulting precipitate was dried to give 5.2 g of a solid. Theweight-average molecular weight and the number-average molecular weightof the polymer were determined by GPC to be 9,900 and 6,100,respectively, against polyethylene glycol standards.

Preparation B6 Preparation of Waterfastness-imparting Agent B6

A 500-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 19.7g of N,N-dimethylaminopropylacrylamide, 81.3 g of a 75 wt % aqueoussolution of (3-acrylamidopropyl)trimethylammonium chloride, 4.0 g of2,4-diphenyl-4-methyl-1-pentene, and 130 g of N,N-dimethylformamide. Asolution of 5.0 g of dimethyl 2,2′-azobis(2-methyl propionate) dissolvedin 20 g of N,N-dimethylformamide was then added to the flask. Thereaction mixture was heated to 80° C. while stirring under a nitrogenatmosphere, and the solution was kept at 80° C. for 4 hr. The reactionsolution was then heated to 95° C., and the reaction was continued foradditional 2 hr at 95° C., followed by cooling to room temperature togive about 260 g of a pale yellow solution. The solvent was removedunder the reduced pressure. A highly viscous liquid as the residue wasdissolved in methanol, and a precipitation procedure from a mixture ofmethanol and acetone was repeated several times. The resultingprecipitate was dried to give 60.1 g of a solid.

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of water and 10.0 g of the solid prepared above. The reaction mixturewas heated to 90° C. while stirring under a nitrogen atmosphere, and thereaction solution was then kept at 90° C. for 20 hr, followed by coolingto room temperature. Thus, about 30 g of a pale yellow transparentsolution was prepared. The solvent was removed under the reducedpressure. The residue was redissolved in methanol, and a precipitationprocedure from a mixture of methanol and acetone was repeated severaltimes. The resulting precipitate was dried to give 8.1 g of a solid. Theweight-average molecular weight and the number-average molecular weightof the polymer were determined by GPC to be 4,600 and 3,100,respectively, against polyethylene glycol standards.

Preparation B7 Preparation of Waterfastness-imparting Agent B7

A 100-ml flask equipped with a thermometer, a stirring device, anitrogen introduction tube, and a reflux condenser was charged with 20.0g of a 75 wt % aqueous solution of (3-acrylamidopropyl)trimethylammoniumchloride, 2.26 g of 2,4-diphenyl-4-methyl-1-pentene, and 20.0 g ofN,N-dimethylformamide. A solution of 1.35 g of dimethyl2,2′-azobis(2-methyl propionate) dissolved in 20.0 g ofN,N-dimethylformamide was then added to the flask. The reaction mixturewas heated to 80° C. while stirring under a nitrogen atmosphere, and thesolution was kept at 80° C. for 4 hr. The reaction solution was thenheated to 95° C., and the reaction was continued for additional 2 hr at95° C., followed by cooling to room temperature to give about 63 g of aturbid pale yellow solution. The solvent was removed under the reducedpressure. A highly viscous liquid as the residue was dissolved inmethanol, and a precipitation procedure from a mixture of methanol andacetone was repeated several times. The resulting precipitate was driedto give 12.3 g of a solid. A 100-ml flask equipped with a thermometer, astirring device, a nitrogen introduction tube, and a reflux condenserwas charged with 20.0 g of water and 10.0 g of the solid prepared above.The reaction mixture was heated to 90° C. while stirring under anitrogen atmosphere, and the solution was then kept at 90° C. for 20 hr,followed by cooling to room temperature. Thus, about 30 g of a paleyellow transparent solution was prepared. The solvent was removed underthe reduced pressure. The residue was redissolved in methanol, and aprecipitation procedure from a mixture of methanol and acetone wasrepeated several times. The resulting precipitate was dried to give 8.5g of a solid. The weight-average molecular weight and the number-averagemolecular weight of the polymer were determined by GPC to be 14,000 and5,700, respectively, against polyethylene glycol standards.

Color Ink Set B1

C.I. Direct Black 195 (6 g), 10 g of glycerin, 10 g of diethyleneglycol, and 5 g of 2-pyrrolidone were mixed together. Ultrapure waterwas added to the mixture to bring the total amount of the mixture to 100g, followed by filtration through a 5-μm filter to give a black ink B1.

A yellow ink B1, a magenta ink B1, and a cyan ink B1 were prepared inthe same manner as above, except that the dye was changed to 2.5 g ofC.I. Direct Yellow 132 for the yellow ink B1, 2 g of C.I. Acid Red 249for the magenta ink B1, and 4 g of C.I. Direct Blue 199 for he cyan inkB1.

These four color inks were combined to give a color ink set B1.

Color ink set B2

C.I. Food Black 2 (10 g), 15 g of glycerin, 5 g of diethylene glycolmonobutyl ether, 5 g of diethylene glycol, and 1 g of a nonionicsurfactant Surfynol 465 (tradename; manufactured by Air Products andChemicals Inc.) were mixed together. Further, ultrapure water was addedto bring the total amount of the mixture to 100 g. Thus, a black ink B2was prepared.

Yellow ink B2, magenta ink B2, and cyan ink B2 were prepared in the samemanner as above, except that the dye was changed to 5 g of C.I. AcidYellow 23 for the yellow ink B2, 2.5 g of C.I. Direct Red 9 for themagenta ink B2, and 4 g of C. I. Direct Blue 87 for the cyan ink B2.

These four color inks were combined to give a color ink set B2.

Color Ink Set B3

A carbon black MA 7 (tradename; manufactured by Mitsubishi ChemicalCorporation) (5 g), 1 g of a styrene-acrylic acid copolymer (tradename:Joncryl 679, Mw 7,000, acid value 200, manufactured by Johnson PolymerCorp.), and 0.3 g of triethanolamine were mixed together. The mixture,together with glass beads (diameter 1.7 mm, 82.5 g), was dispersed in asand mill (manufactured by Yasukawa Seisakusho) for 2 hr. Thereafter,the glass beads were removed. Voncoat 4001 (tradename; acrylic resinemulsion, resin component 50% by weight, manufactured by Dainippon Inkand Chemicals, Inc.) (50 g), 0.7 g of sucrose, 6.3 g of maltitol, 10 gof glycerin, 2 g of 2-pyrrolidone, and 4 g of ethanol were addedthereto, followed by the addition of ultrapure water to bring the totalamount of the mixture to 100 g and mixing with stirring. The mixture wasthen filtered through a 5-μm filter to give a black ink B3.

A yellow ink B3, a magenta ink B3, and a cyan ink B3 were prepared inthe same manner as above, except that the pigment was changed to 2 g ofa pigment Ket Yellow 403 (tradename; manufactured by Dainippon Ink andChemicals, Inc.) for the yellow ink B3, 2 g of a pigment Ket Red 309(tradename; manufactured by Dainippon Ink and Chemicals, Inc.) for themagenta ink B3, and 2 g of a pigment Ket Blue EX-1 (tradename;manufactured by Dainippon Ink and Chemicals, Inc.) for the cyan ink B3.

These four color inks were combined to give a color ink set B3.

Color Ink Set B4

C.I. Direct Black 19 (6 g), 10 g of glycerin, 10 g of diethylene glycol,7 g of triethylene glycol monobutyl ether, 0.1 g of sodium alginate(manufactured by Kanto Kogyo K.K.), and 0.8 g of a nonionic surfactantSurfynol 465 (tradename; manufactured by Air Products and ChemicalsInc.) were mixed together. Further, ultrapure water was added to bringthe total amount of the mixture to 100 g, followed by filtration througha 5-μm filter to give a black ink B4.

Yellow ink B4, magenta ink B4, and cyan ink B4 were prepared in the samemanner as above, except that the dye was changed to 2.5 g of C.I. DirectYellow 144 for the yellow ink B4, 2 g of C.I. Direct Red 227 for themagenta ink B4, and 4 g of C.I. Acid Blue 9 for the cyan ink B4.

These four color inks were combined to give a color ink set B4.

Color Ink Set B5 Preparation of Ink Set B5

To 2.0 g of the waterfastness-imparting agent B1prepared in PreparationB1 were added 4 g of C.I. Acid Black 24, 11 g of glycerin, 5 g of2-pyrrolidinone, and 10 g of diethylene glycol monobutyl ether. Further,ultrapure water was added to bring the total amount of the mixture to100 g. Thus, a black ink B5 was prepared.

Yellow ink B5, magenta ink B5, and cyan ink B5 were prepared in the samemanner as above, except that the dye was changed to 3 g of C.I. AcidYellow 23 for the yellow ink B1, 2 g of C.I. Acid Red 13 for the magentaink B1, and 2.5 g of C.I. Acid Blue 9 for the cyan ink B1.

These four inks were combined to give ink set B5.

Reaction Solution B1

The waterfastness-imparting agent B1 (4 g) prepared in Preparation B1,10 g of glycerin, 10 g of diethylene glycol, and 5 g of diethyleneglycol monobutyl ether were mixed together. Ultrapure water was added tothe mixture to bring the total amount of the mixture to 100 g, followedby filtration through a 5-μm filter to give a reaction solution B1.

Reaction Solution B2

A reaction solution B2 was prepared in the same manner as describedabove in connection with the reaction solution B1, except that thewaterfastness-imparting agent was changed to 7 g of thewaterfastness-imparting agent B6 prepared in Preparation B6 and 8 g of35% hydrochloric acid was additionally used.

Reaction Solution B3

A reaction solution B3 was prepared in the same manner as describedabove in connection with the reaction solution B1, except that thewaterfastness-imparting agent was changed to 6 g of thewaterfastness-imparting agent B5 prepared in Preparation B5 and 5 g ofmagnesium nitrate hexahydrate was used as a polyvalent metal salt.

Reaction Solution B4

A reaction solution B4 was prepared in the same manner as describedabove in connection with the reaction solution B1, except that thewaterfastness-imparting agent was changed to 5 g of the waterfastness-imparting agent B7 prepared in Preparation B7 and, in addition, 7 g of35% hydrochloric acid and 5 g of magnesium nitrate hexahydrate as apolyvalent metal salt were used.

Reaction Solution B5

The waterfastness-imparting agent B3 (7 g) prepared in Preparation B3, 8g of 35% hydrochloric acid, 10 g of glycerin, and 10 g of diethyleneglycol were mixed together. Ultrapure water was added to the mixture tobring the total amount of the mixture to 100 g, followed by filtrationthrough a 5-μm filter to give a reaction solution B5.

Example B1

The color ink set B1 was used in combination with the reaction solutionB2, and, for this combination, the following tests on evaluation ofproperties were carried out.

Example B2

The color ink set B2 was used in combination with the reaction solutionB1, and, for this combination, the following tests on evaluation ofproperties were carried out.

Example B3

The color ink set B3 was used in combination with the reaction solutionB4, and, for this combination, the following tests on evaluation ofproperties were carried out.

Example B4

The color ink set B4 was used in combination with the reaction solutionB3, and, for this combination, the following tests on evaluation ofproperties were carried out.

Example B5

The color ink set B1 was used in combination with the reaction solutionB5, and, for this combination, the following tests on evaluation ofproperties were carried out.

Example B6

The color ink set B2 was used in combination with the reaction solutionB5, and, for this combination, the following tests on evaluation ofproperties were carried out.

Example B7

The color ink set B5 was used in combination with the reaction solutionB5, and, for this combination, the following tests on evaluation ofproperties were carried out.

Example B8 (Comparative)

Only color ink set B1 was provided, and, for the color ink set B1, thefollowing tests on evaluation of properties were carried out.

Example B9 (Comparative)

Only color ink set B3 was provided, and, for the color ink set B3, thefollowing tests on evaluation of properties were carried out.

Example B10 (Comparative)

A reaction solution B6 was prepared in the same manner as describedabove in connection with the reaction solution B1, except that 4 g (on asolid basis) of PAA-10 (tradename; a 10% aqueous solution ofpolyallylamine, manufactured by Nitto Boseki Co., Ltd.) was used as thewaterfastness-imparting agent. The reaction solution B6 was used incombination with the color ink set B1, and, for this combination, thefollowing tests on evaluation of properties were carried out.

Tests on Evaluation of Properties

The color ink sets prepared above were used in combination with thereaction solutions prepared above, and these combinations were evaluatedby the following methods. An ink jet recording printer (a color printerPM-750C, manufactured by Seiko Epson Corporation) was modified and usedin this test.

Evaluation test B1 Print Quality (Feathering and Color Bleeding)

Two types of plain papers (tradename: Xerox P and Xerox 4024; bothproducts being manufactured by Fuji Xerox Co., Ltd.) of size A4 andrecycled paper (tradename: Xerox R, manufactured by Fuji Xerox Co.,Ltd.) of size A4 were provided as recording media. For Examples B1 to B6and B10, two evaluation tests were carried out. Specifically, in one ofthe two evaluation tests, the reaction solution was first printed, and,immediately after that, a full-color image was printed using the colorink set. In the other evaluation test, printing was first carried outusing the color ink set, and, immediately after that, the reactionsolution was printed. The full-color images thus obtained were visuallyinspected for feathering and color bleeding. The results were evaluatedaccording to the following criteria.

A: For all the recording media, neither feathering nor color bleedingwas observed.

B: For some recording media, slight feathering or color bleeding wasobserved.

C: For all the recording media, significant feathering or color bleedingwas observed.

Evaluation Test B2 Waterfastness

The same recording medium and printer as used in the evaluation test B1were provided, and, for combinations specified in the examples and thecomparative examples, 1.5 cm-width black, yellow, magenta, cyan, red,green, and blue full blotted images and letters were printed atintervals of 3.5 cm (nonrecorded area). The prints thus obtained wereallowed to stand under natural environment for one hr, and then immersedin 500 ml of water for one hr. After the immersion, the prints weredried under natural environment for 24 hr, and the density of thetransfer of the ink onto the nonrecorded area and the residue of the inkon the recorded area were visually inspected. The results were evaluatedaccording to the following criteria.

A: The nonrecorded area was not colored at all, and there was no changein the recorded area.

B: In some cases, there was coloration of the nonrecorded area and alowering in color density in the recorded area.

C: Coloration of the nonrecorded area and a lowering in color density inthe recorded area significantly occurred, and, in particular, lettersdisappeared and were illegible.

Evaluation Test B3 Lightfastness

The same recording medium and printer as used in the evaluation test B1were provided, and, for combinations specified in the examples and thecomparative examples, full-color images were printed. For the printsthus obtained, the O.D. value was measured with a color control systemSPM 50 (tradename; manufactured by Gretag), before and after exposure tolight for one day by means of a xenon fadeometer Ci35W (tradename;manufactured by Atlas Electric Device). The results were evaluatedaccording to the following criteria.

A: Color change and fading of less than 5% in terms of O.D. value

B: Color change and fading of 5 to 20% in terms of O.D. value

C: Color change and fading of more than 20% in terms of O.D. value

The results were as summarized in the following table.

TABLE 2 Print quality (Printing before deposition of reaction solution)/(Printing after deposition of Water- Light- Example reaction solution)fastness fastness B1 A/B A A B2 A/A A A B3 A/B A A B4 A/A A A B5 A/A A AB6 A/A A A B7 A/A A A B8 C C A B9 C B A B10 A/B A C

What is claimed is:
 1. A waterfastness-imparting agent comprising acationic water-soluble resin, said cationic water-soluble resincomprising a (co)polymer of, in formula (I), repeating units (a)represented by formula (a) and repeating units (b) represented byformula (b), the content of the repeating units (a) in the (co)polymerbeing 100 to 0% by mole, said (co)polymer having in its molecule acarboxyl-containing group as one of the terminal groups and an aromaticring-containing group as the other terminal group:

wherein R₁ represents a hydrogen atom or a methyl group; R₂ and R₃,which may be the same or different, represent a C₁₋₃ alkyl group; R₄represents a hydrogen atom or a methyl group; R₅, R₆, and R₇, which maybe the same or different, represent a C₁₋₃ alkyl group; Z⁻ represents acounter ion; and k and l, which may be the same or different, are each1, 2, or
 3. 2. The waterfastness-imparting agent according to claim 1,which has a number average molecular weight of 1,000 to 10,000.
 3. Thewaterfastness-imparting agent according to claim 1, wherein thecarboxyl-containing terminal group is a group selected from the groupconsisting of formulae (II) to (V):


4. The waterfastness-imparting agent according to claim 1, wherein thearomatic ring-containing terminal group is a group selected from thegroup consisting of formulae (VI) to XVII):


5. The waterfastness-imparting agent according to claim 1, wherein theunits (a) and the units (b) are present in a block or random form in thecopolymer.
 6. The waterfastness-imparting agent according to claim 1,wherein, in the repeating units of formula (I), R₁ represents a hydrogenatom and R, represents a hydrogen atom.
 7. The waterfastness-impartingagent according to claim 1, wherein, in the repeating units of formula(I), k is 3 and 1 is
 3. 8. The waterfastness-imparting agent accordingto claim 1, wherein, in the repeating units of formula (I), Z representsa halogen atom.
 9. An ink composition comprising at least analkali-soluble colorant, a water-soluble organic solvent, water, and thecationic water-soluble resin as defined in claim 1 with the content ofthe units (a) being 100 to 80% by mole.
 10. The ink compositionaccording to claim 9, wherein the cationic water-soluble resin has anumber average molecular weight of 1,000 to 10,000.
 11. The inkcomposition according to claim 9, wherein the carboxyl-containingterminal group in the cationic water-soluble resin is a group selectedfrom the group consisting of formulae (II) to (V):


12. The ink composition according to claim 9, wherein the aromaticring-containing terminal group in the cationic water-soluble resin is agroup selected from the group consisting of formulae (VI) to (XVII):


13. The ink composition according to claim 9, wherein the cationicwater-soluble resin is a block or random copolymer of the units (a) withthe units (b).
 14. The ink composition according to claim 9, wherein, inthe repeating units represented by formula (I), R₁ represents a hydrogenatom and R₄ represents a hydrogen atom.
 15. The ink compositionaccording to claim 9, wherein, in the repeating units of by formula (I),k is 3 and 1 is
 3. 16. The ink composition according to claim 9,wherein, in the repeating units of formula (I), Z represents a halogenatom.
 17. The ink composition according to claim 9, which furthercomprises an acidic material.
 18. The ink composition according to claim9, which further comprises a basic material.
 19. The ink compositionaccording to claim 18, wherein the basic material is a hydroxide of analkali metal or a hydroxide of an alkaline earth metal.
 20. The inkcomposition according to claim 9, wherein the water-soluble organicsolvent has a vapor pressure which is lower than that of water.
 21. Theink composition according to claim 9, which comprises 5 to 50% by weightof the water-soluble organic solvent.
 22. The ink composition accordingto claim 9, which further comprises a penetration accelerator selectedfrom the group consisting of lower alcohols, cellosolves, carbitols, andnonionic surfactants.
 23. The ink composition according to claim 9,which further comprises a nonionic surfactant and at least one memberselected from the group consisting of lower alcohols, cellosolves, andcarbitols.
 24. The ink composition according to claim 9, wherein thecolorant is a dye or a pigment.
 25. The ink composition according toclaim 9, which further comprises a water-soluble resin other than thecationic water-soluble resin.
 26. The ink composition according to claim9, which further comprises a clogging preventive selected from the groupconsisting of water-soluble hydroxypyridine derivatives, chain or cyclicamide compounds, imidazole derivatives, hydroxy cyclic amine compounds,azole compounds, azine compounds, amidine derivatives, and purinederivatives.
 27. The ink composition according to claim 9, which is usedin ink jet recording.
 28. A reaction solution for ink jet recordingmethod which comprises the step of depositing a reaction solution and anink composition onto a recording medium to perform printing, saidreaction solution comprising at least the cationic water-soluble resinas defined in claim
 1. 29. The reaction solution according to claim 28,wherein the cationic water-soluble resin has a number average molecularweight of 1,000 to 10,000.
 30. The reaction solution according to claim28, wherein the carboxyl-containing terminal group in the cationicwater-soluble resin is a group selected from the group consisting offormulae (II) to (V):


31. The reaction solution according to claim 28, wherein the aromaticring-containing terminal group in the cationic water-soluble resin is agroup selected from the group consisting of formulae (VI) to (XVII):


32. The reaction solution according to claim 28, wherein the cationicwater-soluble resin is a block or random copolymer of the units (a) withthe units (b).
 33. The reaction solution for ink jet recording accordingto claim 28, wherein, in the repeating units of formula (I) constitutingthe cationic water-soluble resin, R₁ represents a hydrogen atom and R₄represents a hydrogen atom.
 34. The reaction solution for ink jetrecording according to claim 28, wherein, in the repeating units offormula (I) constituting the cationic water-soluble resin, k is 3 and 1is
 3. 35. The reaction solution for ink jet recording according to claim28, wherein, in the repeating units of formula (I) constituting thecationic water-soluble resin, Z represents a halogen atom.
 36. Thereaction solution for ink jet recording according to claim 28, whichfurther comprises an acidic material.
 37. The reaction solution for inkjet recording according to claim 28, which further comprises a basicmaterial.
 38. The reaction solution for ink jet recording according toclaim 37, wherein the basic material is a hydroxide of an alkali metalor a hydroxide of an alkaline earth metal.
 39. The reaction solution forink jet recording according to claim 28, which further comprises awater-soluble resin other than the cationic water-soluble resin.
 40. Thereaction solution for ink jet recording according to any one of claims28 to 39, which further comprises a polyvalent metal salt.
 41. Thereaction solution for ink jet recording according to claim 40, whereinthe polyvalent metal salt is a nitrate or a carboxylate.
 42. Thereaction solution for ink jet recording according to claim 28, which hasa pH value of 2 to
 10. 43. An ink jet recording method comprising thestep of depositing an ink composition and the reaction solutionaccording to claim 28, onto a recording medium to perform printing. 44.The ink jet recording method according to claim 43, wherein the inkcomposition comprises a pigment or a dye as a colorant.
 45. The ink jetrecording method according to claim 43, wherein the ink. compositioncomprises the pigment and a resin emulsion.
 46. The ink jet recordingmethod according to claim 43, wherein the step of ejecting droplets ofthe ink composition onto the recording medium is carried out after thestep of depositing the reaction solution onto the recording medium. 47.The ink jet recording method according to claim 43, wherein the step ofejecting droplets of the ink composition onto the recording medium iscarried out before the step of depositing the reaction solution onto therecording medium.
 48. The ink jet recording method according to claim43, wherein the ink composition comprises at least an alkali-solublecolorant, a water-soluble organic solvent, water, and the cationicwater-soluble resin comprising a (co)polymer of, in formula (I),repeating units (a) represented by formula (a) and repeating units (b)represented by formula (b), the content of the repeating units (a) inthe (co)polymer being 100 to 0% by mole, said (co)polymer having in itsmolecule a carboxyl-containing group as one of the terminal groups andan

aromatic ring-containing group as the other terminal group:  wherein R₁represents a hydrogen atom or a methyl group; R₂ and R₃, which may bethe same or different, represent a C₁₋₃ alkyl group; R₄ represents ahydrogen atom or a methyl group; R₅, R₆, and R₇ which may be the same ordifferent, represent a C₁₋₃ alkyl group; Z⁻ represents a counter ion;and k and 1, which may be the same or different, are each 1, 2, or 3with the content of the units (a) being 100 to 80% by mole.
 49. A recordproduced by the recording method according to claim 43.